OF  THE 

UNIVERSITY 


Boiler  Accessories 


A  Complete  and  Authoritative  Treatise 

ON   THE  VARIOUS  ACCESSORIES   OF  THE   BOILER    ROOM  AND    ENGINE  ROOM 

ESSENTIAL  TO  ECONOMICAL  OPERATION,   TOGETHER  WITH 

PRACTICAL    INSTRUCTION    IN   THEIR   USE 


By  WALTER  S.  LELAND,  S.  B. 

Assistant  Professor  of  Naval  Architecture,  Massachusetts  Institute 

of  Technology;  American  Society  of  Naval  Archi- 
.  tects  and  Marine  Engineers 


ILLUSTRATED 


CHICAGO 

AMERICAN  SCHOOL  OF  CORRESPONDENCE 
1909 


COPYRIGHT  1908  BY 
AMERICAN  SCHOOL  OF  CORRESPONDENCE 


Entered  at  Stationers'  Hall,  London 
All  Rights  Reserved 


Foreword 


recent  years,  such  marvelous  advances  have  been 
made  in  the  engineering  and  scientific  fields,  and 
so  rapid  has  been  the  evolution  of  mechanical  and 
constructive  processes  and  methods,  that  a  distinct 
need  has  .been  created  for  a  series  of  practical 
working  guides,  of  convenient  size  and  low  cost,  embodying  the 
accumulated  results  of  experience  and  the  most  approved  modern 
practice  along  a  great  variety  of  lines.  To  fill  this  acknowledged 
need,  is  the  special  purpose  of  the  series  of  handbooks  to  which 
this  volume  belongs. 

C,  Iu  the  preparation  of  this  series,  it  has  been  the  aim  of  the  pub- 
lishers to  lay  special  stress  on  the  practical  side  of  each  subject, 
as  distinguished  from  mere  theoretical  or  academic  discussion. 
Each  volume  is  written  by  a  well-known  expert  of  acknowledged 
authority  in  his  special  line,  and  is  based  on  a  most  careful  study 
of  practical  needs  and  up-to-date  methods  as  developed  under  the 
conditions  of  actual  practice  in  the  field,  the  shop,  the  mill,  the 
power  house,  the  drafting  room,  the  engine  room,  etc. 

C,  These  volumes  are  especially  adapted  for  purposes  of  self- 
instruction  and  home  study.  The  utmost  care  has  been  used  to 
bring  the  treatment  of  each  subject  within  the  range  of  the  com- 


179743 


mon  understanding,  so  that  the  work  will  appeal  not  only  to  the 
technically  trained  expert,  but  also  to  the  beginner  and  the  self- 
taught  .practical  man  who  wishes  to  keep  abreast  of  modern 
progress.  The  language  is  simple  and  clear;  heavy  technical  terms 
and  the  formulae  of  the  higher  mathematics  have  been  avoided, 
yet  without  sacrificing  any  of  the  requirements  of  practical 
instruction;  the  arrangement  of  matter  is  such  as  to  carry  the 
reader  along  by  easy  steps  to  complete  mastery  of  each  subject; 
frequent  examples  for  practice  are  given,  to  enable  the  reader  to 
test  his  knowledge  and  make  it  a  permanent  possession;  and  the 
illustrations  are  selected  with  the  greatest  care  to  supplement  and 
make  clear  the  references  in  the  text. 

C.  The  method  adopted  in  the  preparation  of  these  volumes  is  that 
which  the  American  School  of  Correspondence  has  developed  and 
employed  so  successfully  for  many  years.  It  is  not  an  experiment, 
but  has  stood  the  severest  of  all  tests — that  of  practical  use — which 
has  demonstrated  it  to  be  the  best  method  yet  devised  for  the 
education  of  the  busy  working  man. 

C,  For  purposes  of  ready  reference  and  timely  information  when 
needed,  it  is  believed  that  this  series  of  handbooks  will  be  found  to 
meet  every  requirement. 


Table    of    Contents 


SPECIAL  CONSTRUCTIONS  AND  MECHANICAL  AIDS      .      .       .       Page     1 

Boiler  Setting  —  Supports  —  Foundation  —  Enclosing  Walls — Furnaces — 
Doors — Grates  (Circular,  Herring-Bone,  Rocking,  etc.) — Bridge — Preven- 
tion of  Smoke — Down-Draft  Furnaces — Hollow  Arch — Fuel  Economizers — 
Mechanical  Stokers — Fusible  Plugs — Natural  Draft — Forced  Draft — Draft 
Gauge — Closed  Stoke-Hold  System — Closed  Ash-Pit  System — Induced-Draft 
System — Howden  System — Ellis  &  Eaves  System — Steam  Jets — Tube- 
Cleaners — Tube-Stoppers — Manholes  and  Handholes — Mudholes 


CONTROL  AND  SUPPLY  DEVICES      ..        .        .      ..        .       „       Page    29 

Steam  Gauges  —  Vacuum  Gauges  —  Water  Gauges  —  Try-Cocks  —  Gauge- 
Glasses  —  Valves  (Globe,  Angle,  Gate) —  Check-Valves  —  Safety- Valves 
(Lever,  Pop) — Pop  Regulator — Muffler — Reducing  Valves — Blow-Out  Ap- 
paratus— Surface  and  Bottom  Blow-Outs — Feed  Apparatus — Feed-Pump — 
Donkey  Pump — Duplex  Pump- — Injectors  or  Inspirators — Circulating  Ap- 
paratus— Hydro-kineter — Evaporators — Feed-Water  Heaters — Steam  Sepa- 
rators— Wet  Steam — Superheated  Steam — Priming — Steam  Traps  (Float, 
Bucket,  Differential) — Return  Traps — Equalizing  Valve  —  Calorimeters 
(Barrel,  Separator,  Throttling) — Sampling  Pipe — Piping — Pipe  Line  Sup- 
ports— Expansion  Joints — Lagging — Heat  Losses— rPipe  Coverings — Pre- 
ventives of  Radiation  (Asbestos,  Mineral  Wool,  Felt,  Plaster  of  Paris, 
etc.) — -Boiler  Coverings — Horse-Power  of  Boilers 


BOILER  TROUBLES  AND  TESTS Page    81 

Corrosion  and  Incrustation — Pitting — Grooving — Scale — Sludge — Hard  and 
Soft  Water — Grease  Extractor — Carbonate  of  Lime — Sulphate  of  Lime — 
Carbonate  of  Magnesia — Iron  Salts — Water  Purification — Boiler  Explosions 
- — Boiler  Inspection — Energy  in  Hot  Water — Causes  of  Explosions  (Low 
Water,  Grease,  Scale,  Defective  Design,  Deterioration,  Defective  Workman- 
ship, Mismanagement) — Investigation  of  Explosions — Prevention  of  Explo- 
sions— Fuel — Coal  (Anthracite  and  Bituminous,  Lignite) — Peat — Coke — 
Charcoal — Culm — Wood— Straw — Sawdust — Bagasse — Liquid  Fuel  (Crude 
Petroleum) — Atomizers — Gas  (Natural,  Coal,  Water,  Producer) — Artificial 
Fuels — Boiler  Trials — Records  of  Tests — Firing — Care  of  Boilers 


INDEX Page  119 

OF  THE 

UNIVERSITY 

OF 


MANHATTAN     74TH    ST.     POWER    STATION,     NEW    YORK. 

^bowing  Carey's  Magnesia  Pipe  and  Boiler  Covering. 


BOILER  ACCESSORIES 

PART  I 


BOILER  SETTING 

The  setting  for  a  stationary  boiler  consists  of  the  foundation  and 
as  much  of  the  furnace  and  flues  as  is  external  to  the  boiler  shell.  Some 
internally-fired  boilers — the  "Lancashire,"  for  instance — have  flues  in 
the  brick  setting.  The  whole  furnace  and  sometimes  the  flues,  as  is 
the  case  with  the  plain  cylindrical  boiler,  are  in  the  setting.  Vertical 
boilers  have  simply  a  foundation;  and  locomotive  boilers  have  no 
setting,  since  they  are  supported  by  the  frames  of  the  engines.  Marine 
boilers  are  usually  placed  on  saddles,  which  are  built  into  the  framing 
of  the  vessel. 

In  setting  a  boiler,  there  are  three  principal  requisites  that  should 
be  kept  in  mind :  1.  A  stable  support  or  foundation  for  the  shell,  so 
arranged  as  to  allow  for  proper  expansion  of  the  boiler.  2.  Properly 
arranged  spaces  for  both  furnace  flues  and  ash-pit.  3.  A  covering 
which  will  prevent  loss  of  heat  by  radiation,  and  which  will  not  allow 
moisture  to  accumulate  in  contact  with  the  plates. 

There  are  two  principal  methods  for  support — by  brackets 
riveted  to  the  shell  plates,  and  by  suspension  from  overhead  girders 
by  means  of  .hooks,  rings,  etc.  In  any  case  the  supports  should  be 
so  arranged  that  each  shall  bear  its  proper  proportion  of  the  load  and 
at  the  same  time  allow  for  expansion.  If  the  boiler  is  short,  brackets 
are  generally  used;  while  for  long,  plain  cylindrical  boilers  the  girder 
method  is  the  more  common.  If  a  very  long,  cylindrical  boiler  is 
supported  only  at  each  end,  the  great  weight  between  the  two  sup- 
ports is  likely  to  cause  bending  and  an  excessive  strain  on  the  middle 
plates,  tension  in  the  bottom  plates,  and  compression  in  the  top  plates. 

The  first  requisite  for  a  setting  is  a  good  foundation.  If  the 
ground  is  firm  and  favorable  to  a  solid  foundation,  the  excavation 
need  be  only  three  or  four  feet  below  the  level.  If  it  is  soft,  the  exca- 
vation should  be  deeper,  and  the  extra  depth  filled  in  with  broken 
stone  mixed  in  with  cement,  gravel,  etc. ;  or,  for  very  heavy  work, 


BOILER  ACCESSORIES 


piles  may  be  driven.  The  first  course  of  the  foundation  should  be 
large  stones  laid  in  cement;  upon  this  stonework  the  walls  may  be 
built,  either  of  stone  or  brick,  to  within  about  six  inches  of  the  floor- 
level;  and  above  this,  brick  should  be  used. 

Sometimes  the  bed  is  made  of  concrete  about  two  feet  .in  thick- 
ness. If  the  soil  is  very  firm,  a  foundation  of  large  stonework  about 
three  feet  wide  may  be  built  under  the  side,  middle,  and  end  walls  only. 

In  determining  the  area  of  the  bed,  the  weight  that  is  to  be  put 
on  each  square  foot  should  be  estimated  carefully.  With  ordinary 
condition  of  the  soil,  this  should  not  exceed  2,000  pounds.  For 
greater  weights,  special  construction  must  be  used. 

The  supporting  and  enclosing  walls  are  built  upon  the  foundation, 
with  the  outer  walls  at  the  sides  and  rear  double,  the  space  between, 
usually  about  two  inches,  being  an  air-space  insulation  to  prevent 
loss  of  heat.  Projecting  bricks,  which  extend  from  the  outer  until  they 
just  touch  the  inner  wall,  allow  for  expansion  without  decreasing  the 
strength  of  the  inner  wall.  The  side  walls  are  strengthened  by  buck- 
stays  or  binders,  which  are  kept  in  place  by  long  bolts,  secured  by 
nuts  on  each  end.  Fig.  1  shows  a  boiler  in  the  brick  setting,  sup- 
ported by  brackets,  the  front  brackets  resting  on  iron  plates  which 
are  built  into  the  walls;  the  rear  brackets,  being  supported  by  rollers, 
are  free  to  move  as  the  shell  expands.  If  designed  for  anthracite 
coal,  the  distance  between  the  shell  and  the  grate-bars  is  about  two 
feet;  for  softer  coal,  this  distance  is  increased  a  few  inches. 

The  furnace  is  lined  with  firebrick,  both  front  and  sides ;  and 
sometimes  portions  back  of  the  bridge,  as  well  as  the  bridge  itself, 
may  thus  be  protected.  The  space  between  the  bridge  and  the  shell 
is  from  6  to  8  inches,  which  brings  the  hot  gases  into  close  contact 
with  the  boiler  before  they  enter  the  combustion  chamber  beyond, 
the  rear  and  side  walls  being  built  a  little  higher  than  the  top  row  of 
tubes.  The  fire-line  must  not  be  carried  above  the  water-line;  if  it 
is,  the  intense  heat  is  likely  to  injure  the  shell-plates.  Never  expose 
any  part  of  the  boiler  not  covered  by  water  to  the  flames  from  the 
furnace.  The  side  walls  are  built  about  the  same  height  as  the  rear 
walls.  The  space  at  the  rear  is  bridged  over  and  stiffened  by  T-irons. 
In  order  to  increase  the  heating  surface,  the  top  is  arched  so  that  the 
hot  gases  will  pass  over  the  steam  space  before  they  enter  the  chimney. 


BOILER  ACCESSORIES 


BOILER  ACCESSORIES 


The  smoke  box  projects  over  the  front  end  of  the  boiler  and  has 
a  rectangular  uptake. 

Fig.  3  shows  the  top  view  of  the  same  boiler. 

The  front  is  usually  of  cast  iron,  with  doors  for  firing  and  cleaning 
and  for  access  to  the  tubes.  Soot,  dirt,  etc.,  are  removed  through  the 
door  in  the  brickwork  at  the  rear. 

The  end  which  contains  the  handhole  should  be  set  about  one 


Fig.  2.    Front  Elevation  of  Boiler  in  Setting,  Showing  Binders  Bolted  in 
Place,  to  Strengthen  Side  Walls. 

inch  lower  than  the  other  end,  so  that  the  sediment  and  detached  scale 
will  tend  to  accumulate  there. 

Internally-fired  boilers  may  also  be  enclosed  in  brickwork.  The 
setting  is  a  support  and  covering,  forming  the  side  flues  but  not  the 
furnace.  Excess  of  brickwork  surface  in  contact  with  the  shell, 
should  be  avoided,  as  brickwork  collects  moisture,  which  causes 
external  corrosion. 


BOILER  ACCESSORIES 


6 


BOILER  ACCESSORIES 


Water-Tube  Boilers.     The  settings  for  water-tube  boilers  are 
similar  to  the  settings  of  cylindrical  tubular  boilers.     Marine  water- 


Fig.  4.  Fig.  5. 

Types  of  Brackets  for  Supporting  Boilers. 

In  Fig.  4  the  rivets  are  all  above  the  flange;  in  Fig.  5  they  are  both  above 
and  below  the  flange. 

tube  boilers  are  enclosed  in  sheet-iron  casing,  which  is  lined  with  non- 
conducting material,  usually  asbestos  or  m  agnesia. 

Supports.  There  are,  as  already  intimated,  two  common  methods 
of  supporting  boilers — 1.  By  means  of  brackets;  2.  By  suspending 
from  wroughl-ir&n  beams. 

If  the  boiler  is  about  15  feet  long,  it  is  customary  to  use  two 
brackets  on  each  side.  If  more  than  15  feet,  three  on  each  side  are 
used.  The  front  brackets  rest  on  the  brickwork,  but  the  others  rest 
on  small  iron  rollers  to  allow  for  expansion.  Brackets  are  so  arranged 
that  the  plane  of  support  will  be  a  little  above  the  middle.  There  are 
several  forms  of  brackets.  The  form  shown  in  Fig.  4  is  usually  made 
of  cast  iron,  and  is  provided  with  rivets  above  the  flange  of  the  bracket. 


Fig.  6.  Fig.  7. 

Two  Methods  of  Supporting  Boilers  by  Suspending  from  Overhead  Beams. 

It  is  better  to  have  the  rivets  both  above  and  below  the  flange,  as  shown 
in  Fig.  5. 


BOILER  ACCESSORIES 


Fig.  6  shows  one  method  of  suspending  from  beams.  A  lug, 
made  of  wrought  iron,  is  riveted  to  the  plates  of  the  boiler.  A  bolt 
having  one  end  bent  like  a  hook,  holds  the  lug  from  the  beam.  In 
Fig.  7  the  lug  is  replaced  by  a  loop  of  wrought  iron.  Fig.  8  shows 
another  method  of  suspension,  the  connection  between  the  rod  and 
the  boiler-plates  being  short  pieces  of  boiler-plate  arranged  for  flexi- 
bility. 

When  the  boiler  is  of  small  diameter,  it  may  be  suspended  as 
shown  in  Fig.  9. 

*  FURNACES 

To  get  the  maximum  efficiency  from  any  boiler,  it  is  necessary 
that  the  fuel  shall  be  properly  consumed,  and  that  the  proportions 


o  o 
o  o 
o  o 


Fig.  8.    Flexible  Support  for  Suspended  Boiler.    Fig.  9.    Illustrating  Method  of  Suspend- 
Flexibility  Secured  by  means  of  Two  ing  Boiler  of  Small  Diameter. 

Pieces  of  Boiler-Plate  Bolted 
Together. 

of  the  furnace  shall  be  such  as  to  give  the  maximum  results.  No 
boiler  is  economical  the  furnace  of  which  is  so  small  that  the  fire  has 
to  be  forced  to  obtain  the  desired  result.  The  furnace,  of  course,  will 
vary  in  shape,  size,  and  detail  with  the  type  of  boiler  and  the  kind  of 
fuel;  but  certain  essentials — such  as  doors,  grate-bars,  bridge,  and 
ash-pit — are  similar  in  all  furnaces.  To  obtain  the  maximum  effi- 


8  BOILER  ACCESSORIES 

ciency  of  combustion,  there  should  be  a  uniform  and  abundant  supply 
of  air  to  the  under  side  of  the  grate.  This  is  easily  obtained  when  the 
boilers  are  externally  fired,  but  may  be  somewhat  restricted  when  they 
are  internally  fired.  If  smoky  fuels  are  used,  a  moderate  supply  of 
air  is  necessary  on  the  surface  of  the  coal,  to  prevent  excessive  smoke 
formation;  but,  as  the  air  thus  admitted  is  usually  cold,  the  quantity 
should  be  small,  to  prevent  unnecessary  cooling  of  the  furnace.  This 
air  is  generally  supplied  through  a  draft-plate  in  the  fire-door. 

All  possible  radiation  should,  of  course,  be  prevented.  In  the 
case  of  internally-fired  boilers,  this  radiation  is  not  likely  to  be  exces- 
sive, for  most  of  the  heat  would  have  to  pass  through  the  water  in  the 
boiler  before  radiating,  and  it  is  a  comparatively  easy  matter  to  encase 
such  a  boiler  in  some  sort  of  approved  lagging  which  will  prevent 
most  of  the  heat  from  escaping.  The  case  is  somewhat  different  with 
the  externally-fired  boiler,  where  the  furnace  is  built  in  a  mass  of 
brickwork  below  the  boiler.  In  such  a  furnace  a  considerable  amount 
of  heat  may  radiate  directly  from  the  fire  without  coming  in  contact 
with  the  boiler  or  water  at  all. 

To  allow  for  complete  combustion,  there  should  be  a  sufficient 
space  between  the  grate  and  the  boiler.  In  externally-fired  boilers, 
this  space  may  be  approximately  two  feet.  If  this  distance  is  increased 
beyond  proper  limits,  some  effect  of  the  heat  will  be  lost;  and  if  the 
distance  is  small,  the  plates  are  likely  to  be  damaged,  and  complete 
combustion  impaired.  In  the  internally-fired  boiler,  the  combustion 
space  is  frequently  sacrificed  in  order  to  obtain  a  large  grate  area.  If 
the  space  between  the  grate-bars  and  the  boiler  is  too  small  to  allow 
complete  combustion,  a  combustion  chamber  must  be  provided 
immediately  back  of  the  bridge,  which  will  permit  of  the  complete 
combustion  of  the  gases.  The  ideal  place,  of  course,  for  the  combustion 
chamber,  is  immediately  over  the  grate.  In  locomotive  boilers,  the 
crown  sheet  is  usually  four  to  six  feet  above  the  grate;  but  such  a 
height  is  manifestly  impossible  in  marine  or  other  internally-fired 
boilers,  and  the  combustion  chamber  behind  the  bridge  wall,  in  the 
Scotch  boiler,  partially  compensates  for  the  loss  of  space  immediately 
over  the  grate. 

The  incandescent  fuel  and  unconsumed  gases  should  not  come 
in  contact  with  the  cold  surfaces  of  the  boiler  if  the  most  efficient  com- 


BOILER  ACCESSORIES  9 

bustion  is  desired.  This  condition  is  violated  in  internally-fired 
boilers,  where  the  fire  comes  directly  against  metal  having  water  on  one 
side  of  it.  If  the  flame  is  chilled  by  contact  with  cold  surfaces  before 
the  gases  are  completely  burned,  a  considerable  amount  of  smoke  is 
likely  to  result. 

The  fire-grate  should  be  of  such  dimensions  that  the  fireman  can 
work  efficiently.  A  grate  more  than  six  feet  long  cannot  be  properly 
taken  care  of  at  the  farther  end ;  and  if  the  grate  is  more  than  four 
feet  wide,  two  fire-doors  should  be  provided.  The  height  of  the  grate 
should  be  laid  out  with  proper  reference  to  the  floor,  two  feet  above 
the  floor  being  about  right.  If  the  grate  is  high,  it  is  difficult,  if  not 
impossible,  to  tend  the  fire  properly.  These  conditions  are  dependent, 
not  so  much  upon  the  boiler,  as  upon  the  physical  limitations  of  the 
fireman,  and  of  course  are  eliminated  by  using  the  mechanical  stoker. 

To  the  above  conditions  may  be  added  a  suitable  temperature  in 
the  fire-room.  No  man  can  tend  a  fire  properly  in  excessive  heat. 
In  stationary  work  it  is  not  difficult  to  maintain  proper  conditions  in 
the  fire-room;  but  at  sea,  where  the  supply  of  air  is  necessarily  limited 
to  what  can  come  in  through  small  openings,  it  is  a  different  problem. 
The  fire  space  on  board  ship  is  small ;  and  the  air  coming  through  the 
ventilating  ducts  usually  makes  an  exceedingly  cold  spot  immediately 
under  the  duct  without  producing  much  effect  in  other  parts  of  the 
room. 

Door.  The  furnace  door  is  usually  made  of  cast  iron,  and  is 
supplied  with  a  circular  or  sliding  draft-plate  or  grid,  which  admits 
air  to  the  top  of  the  fire  as  needed.  It  is  usually  protected  by  a  per- 
forated, wrought-iron  baffle-plate  bolted  fa  the  door  casting  inside, 
with  an  air-space  of  two  or  three  inches  between.  This  not  only 
protects  the  cast  iron  of  the  door  from  the  direct  force  of  the  flame, 
but  it  forms  a  chamber  for  the  proper  distribution  of  the  air-supply, 
and  also  helps  to  heat  it  somewhat  before  reaching  the  furnace. 

In  many  of  the  French  torpedo-boats,  a  patent  swinging  door  is 
provided,  set  on  horizontal  hinges  swinging  inwards.  The  door, 
of  course,  must  be  held  open  while  the  stoker  is  tending  the  fire;  but 
in  case  a  tube  blows  out,  it  prevents  the  rapid  escape  of  steam  into  the 
fire-room.  This  is  a  matter  of  much  more  importance  in  the  restricted 
fire-room  commonly  found  on  a  vessel  than  it  would  be  on  land. 

Grate.    The  size  of  grate  will  depend  upon  the  quantity  of  coal 


10  BOILER  ACCESSORIES 

likely  to  be  burned.  For  ordinary  draft,  this  may  be  15  Ibs.  or  upward 
per  square  foot  of  grate  surface  per  hour;  for  forced  draft,  40  to  60 
Ibs. ;  and  in  some  cases  as  much  as  100  Ibs.  per  square  foot  of  grate 
surface  has  been  burned.  If  the  grates  are  long,  they  are  usually 
inclined  slightly  downwards,  say  f  inch  to  the  foot,  which  is  a  great 
assistance  in  firing  and  makes  it  easier  to  keep  fire  on  the  farther  end 
of  the  grate.*  The  grate-bars  are  usually  made  of  cast  iron,  as  this 
material  is  cheaper  than  wrought  iron  and  in  most  instances  lasts  as 
well.  The  bars  are  made  in  various  forms,  according  to  the  fuel 
burned  and  the  shape  of  the  firebox. 

For  large  grates,  the  bars  are  made  singly  or  in  pairs.  For 
smaller  grates,  they  are  made  in  larger  groups.  Grate-bars  should 
not  be  more  than  three  feet  in  length.  The  length  of  grate  can  easily 
be  a  multiple  of  the  length  of  these  bars.  The  bars  have  distance 
'  pieces  at  the  ends,  and  perhaps  in  the  middle,  to  prevent  distortion. 
They  are  usually  3  inches  or  more  in  depth  at  the  middle,  tapering  to 
perhaps  an  inch  or  so  at  the  ends;  and  the  cross-section  is  slightly 
tapered  from  top  to  bottom,  so  that  the  bars  can  easily  be  withdrawn 
from  the  sand  after  casting.  They  are  usually  made  a  trifle  shorter 
than  the  place  in  which  they  fit,  to  allow  for  expansion,  2  per  cent  of 
the  length  of  the  bar  usually  being  sufficient  for  this  purpose.  The 
air-spaces  between  the  bars  are  usually  about  \  inch  in  width.  For 
burning  pea  coal  or  screenings,  a  finer  grate  must  be  used.  For 
anthracite  coal,  the  space  may  be  a  little  larger.  Bituminous  coal, 
which  readily  cakes,  can  have  a  considerable  space  between  the  bars—- 
and this,  indeed,  is  essential  for  a  proper  supply  of  air. 

Fig.  10  shows  a  circular  grate,  such  as  is  placed  in  a  vertical 
boiler.  M  shows  the  style  of  grate-bar  used  in  burning  sawdust  or 
shavings;  N  is  what  is  known  as  the  herring  bone  grate;  and  0  is  a 
group  of  bars  of  the  ordinary  form.  In  locomotives,  and  in  boilers 
where  the  grates  are  subjected  to  extra  hard  usage,  wrought-iron  bars 
may  be  used.  The  point  of  fusion  of  wrought  iron  being  higher  than 
that  of  cast  iron,  the  former  would  possess  a  considerable  advantage 
were  it  not  for  the  fact  that  wrought  iron  will  bend  and  twist  more 
readily  than  cast  iron.  Grates  have  been  made  of  hollow  bars, 
through  which  water  is  caused  to  circulate.  By  this  method  their 

*  The  grates  have  an.  incline  of  a  few  inches,  so  that  the  bed  of  coal  will  be  thicker 
at  the  rear  than  at  the  front;  this  allows  a  more  even  consumption  of  fuel,  as  the  air 
passes  through  the  fire  at  the  bridge  more  freely. 


BOILER  ACCESSORIES 


11 


durability  is  increased,  and  the  water-grate  forms  a  fairly  good' feed- 
water  heater.     This  type  of  grate,  however,  is  expensive. 


Fig.  10.    Types  of  Grates  for  Boilers.     7— Circular  Grate  for  Vertical  Boiler ;  M—  Grate  for 

Burning  Sawdust  or  Shavings;  ^—"Herring-Bone"  Grate.  0— Group 

of  Grate-Bars  of  Ordinary  Form. 

Rocking  Grates.  The  labor  of  breaking  the  clinkers  is  con- 
siderable when  ordinary  fixed  grate-bars  are  used ;  and  to  economize 
this  labor,  various  forms  of  rocking-grates  have  been  devised.  In 


.  -;:;•  .  L  • 

,/',,,.':'••  •'/'/'   '    '       y  '  "•        ',1. •••'''     -i  ;      "••')•        ''•}<'   '         .•  t     ••    "    1   •     •         1    -.  \-    .•'.•//•f'-  \ 


Fig.  11.    "Kelley  Standard"  Rocking  Grate. 

locomotives,  rocking-grates  are  essential;  and  since  the  rate  of  com- 
bustion is  high,  the  fire  must  always  be  kept  in  good  condition;  and 


12 


BOILER  ACCESSORIES 


the  grate,  being  below  the  cab  floor,  cannot  easily  be  reached  by  hand. 
Fig.  11  shows  the  "Kelley  Standard'5  rocking  grate.  Each  bar  is 
made  up  of  a  number  of  separate  leaves,  which  can  be  removed  and 
replaced  without  renewing  the  whole  bar.  When  the  bar  is  moved 
back  and  forth  by  means  of  a  lever  outside  the  brickwork,  the  leaves 
oscillate  through  a  small  angle  and  break  up  the  clinkers. 

Another  form  of  bar,  shown  in.  Fig.  12,  has  proved  v6ry  satis- 
factory. A  and  B  are  two  bars,  the  ends  of  which  are  of  different 
depths.  These  rest  at  each  end  on  a  crank-shaft  C.  As  this  is 
oscillated  by  the  lever  G,  the  alternate  bars  move  up  and  down,  and  the 
clinkers  are  easily  shaken  out. 

Bridge.    The  bridge  is  a  large  wall  or  partition  at  the  back  of  the 


Fig.  12.    Rocking  Grate  Consisting  of  Alternate  Bars  with  Ends  of  Different  Depths 
Resting  on  a  Crank-Shaft  Oscillated  by  a  .Lever. 

grate,  usually  built  of  firebrick  or  cast  iron,  or  of  ordinary  brick 
covered  with'  firebrick.  The  bridge  separates  the  grate  from  the  com- 
bustion chamber,  and  causes  the  gases  to  come  in  close  contact  with 
the  boiler  in  passing  into  the  combustion  chamber.  The  proper 
height  of  the  bridge  will  depend  upon  the  draft.  '  If  the  space  is  nar- 
row between  the  bridge  wall  and  the  boiler,  more  draft  will  be  neces- 
sary to  carry  the  gases  through.  Two  or  more  bridges  may  sometimes 
be  built  in  long  boilers  to  keep  the  gases  in  contact  with  the  shell  as 
long  as  possible. 

Special  Furnaces.  Almost  any  furnace  is  adapted  for  the  use  of 
anthracite  or  bituminous  coal  containing  less  than  20  per  cent  of 
volatile  matter;  but  if  there  is  more  than  this  amount  of  volatile 
matter,  the  heat  is  likely  to  be  so  intense  that  the  fire  should'  not  be 


BOILER  ACCESSORIES  13 

brought  in  direct  contact  with  the  boiler.  If  the  fuel  should  contain 
40  per  cent  of  volatile  matter,  the  furnace  should  be  surrounded  with 
firebrick  and  should  have  a  high  combustion  chamber.  Coal  is  the 
most  common  fuel  used ;  but  wood,  sawdust,  and  straw  are  not  uncom- 
mon fuels.  When  these  are  burned,  there  should  be  plenty  of  room 
in  the  furnace,  and  a  sufficient  supply  of  air  on  top  of  the  fuel.  Saw- 
dust, shavings,  and  fine,  coal  may  be  blown  into  the  furnace  by  an  air- 
blast. 

In  the  West,  crude  petroleum  is  becoming  a  common  fuel.  Ex- 
periments have  shown  that  one  pound  of  crude  oil  is  equivalent  in 
heat  units  to  something  less  than  two  pounds  of  good  coal.  Oil  has. 
many  advantages  as  a  boiler  fuel.  It  is  clean,  gives  a  uniform  heat, 
is  economical,  and  requires  much  less  attention  than  coal.  There  are 
no  ashes  to  handle,  and  one  man  can  easily  tend  two  or  three  times 
the  number  of  furnaces  that  he  could  if  burning  coal.  The  fire  can 
be  start,e/l  and  stopped  instantly;  and  the  supply  of -air  can  be  so  regu- 
lated that,  unless  the  boiler  fs  forced  to  the  limit,  there  will  be  prac- 
tically no  production  of  smoke.  Whether  or  not  oil  is  an  economical 
fuel,  will  depend  upon  the  local  conditions  and  the  market. 

Oil  fuel  is  fed  into  the  furnace  through  a  sprayer  formed,  in 
some  cases  of  two  concentric  conical  tubes.  Compressed  air  or 
steam  entering  through  the  one  tube  draws  the  oil  through  the  other, 
on  the  principle  of  the  atomizer,  and  throws  it  into  the  furnace  in  a 
fine  spray.  For  marine  work,  compressed  air  should  be  used,  as  the 
loss  of  steam  for  this  purpose  would  be  a  matter  of  considerable 
consequence.  Steam,  however,  is  sometimes  used  in  marine  work, 
in  which  case  the  vessel  must  be  equipped  with  an  evaporator  to 
make  up  the  steam  thus  lost.  On  land,  where  fresh  water  is  plenty, 
steam  is  usually  preferred,  and  is  less  expensive  in  first  cost. 

Prevention  of  Smoke.  In  large  cities,  where  the  escape  of  con- 
siderable quantities  of  smoke  is  undesirable,  several  methods  have 
been  devised  either  to  consume  the  smoke  or  to  prevent  its  formation. 
The  cause  of  smoke,  as  we  have  seen,  is  an  insufficiency  in  the  supply 
of  air,  or  perhaps  a  too  abundant  supply  of  cold  air  above  the  fire; 
or,  again,  smoke  may  be  due  to  the  contact  of  the  flame  with  cold 
surfaces.  An  exceedingly  high  temperature  is  necessary  to  consume 
the  finely  divided  particles  of  carbon,  and  anything  that  tends  to  chill 
the  flame  will  cause  smoke. 


14 


BOILER  ACCESSORIES 


The  actual  loss  caused  by  the  escape  of  smoke,  even  when  it 
is  dense  and  black,  has  been  found  to  be  slight,  and  usually  the  appli- 
ance used  for  prevention  costs  more  than  is  saved.  The  alternate 
firing  of  two  furnaces  which  open  into  a  common  combustion  chamber, 
or  the  alternate  firing  of  two  sides  of  the  same  furnace,  produces  a 
slight  gain  if  the  proper  amount  of  air  is  admitted.  But  if,  in  order 
to  burn  the  smoke,  the  bed  in  one  furnace  or  on  one  side  of  a  furnace 
is  allowed  to  become  thin,  there  will  be  no  gain  in  efficiency. 

The  introduction  of  steam  is  an  efficient  method,  but  it  is  likely 
to  cause  a  too  rapid  rate  of  combustion. 

Another  arrangement  to  prevent  the  escape  of  smoke  is  that  by 


Fig.  13.    "Hawley"  Down-Draft  Furnace  Attached  to  Horizontal  Multitubular  Boiler. 
Note  Upper  Grate  Consisting  of  Water  Tubes  Connected  to  Steel  Drums. 

which  the  coal  is  distilled  in  a  small  furnace  which  is  separate  from  the 
boiler.  The  coke  and  gases  thus  made  are  burned  in  the  furnace  of 
the  steam  boiler.  This  device  is  not  altogether  satisfactory,  on  account 
of  the  loss  of  heat  from  the  detached  furnace.  Rather  than  add  any 
smoke-prevention  device,  anthracite  or  coke  may  be  used  instead  of 
bituminous  coal. 

Many  engineers  and  business  men  consider  a  good  fireman  to  be 
the  best  smoke  preventer. 


BOILER  ACCESSORIES  15 

Down-Draft  Furnaces.  In  order  to  increase  economy  and 
capacity,  or  to  prevent  smoke,  a  down-draft  furnace  is  sometimes 
used.  In  this  type  of  furnace,  there  are  two  grates,  one  a  foot  or  more 
above  the  other.  Fresh  coal  is  fed  to  the  upper  grate,  and,  asfit 
becomes  partially  consumed,  falls  through  to  the  grate  below,  where 
the  combustion  is  completed.  The  draft  is  downward  through  the 
upper  grate,  and  upward  through  the  lower,  because  the  connection 
to  the  chininey  is  from  the  space  between  the  grates.  The  volatile 
gases  are  carried  down  through  the  bed  on  the  upper  grate,  and  are 
burned  in  the 
space  below  it, 
where  they  meet 
the  hot  air  drawn 
upward  from  the 
lower  grate.  A 
large  proportion 
of  the  air  for  com- 
bustion enters  the 
door  at  the  upper 
grate.  Tests  on 

tVm     TTnwlov     fnr     Fi§-  14-    Upper  Grate  of  "Hawley"  Down-Draft  Furnace.    The 
'  1CJ  Grate-Bars  are  Water  Tubes  Connected  to  Steel  Drums 

nace  show  that  30 

to  45  pounds  of  coal  per  square  foot  per  hour  can  be  burned  with  good 

results. 

In  the  furnace  made  by  the  Hawley  Down-Draft  Boiler  Com- 
pany, the  grates  are  formed  of  a  series  of  water  tubes  opening  at  the 
ends  into  steel  drums,  shown  in  Figs.  13  and  14,  which  are  connected 
with  the  boiler.  Fig.  13  shows  this  furnace  attached  to  a  horizontal, 
multitubular  boiler.  It  may  be  applied  to  both  tubular  and  water- 
tube  boilers  with  good  results,  and  is  advantageous  to  boilers  of  insuf- 
ficient heating  surface,  and  when  inferior  fuels  are  burned.  It  is 
claimed  that  this  attachment  insures  complete  combustion,  small 
amount  of  ashes  on  account  of  the  second  grate,  good  water  circula- 
tion, and  increased  economy  and  capacity. 

The  Hollow  Arch.  Among  boiler  accessories  specially  adapted 
for  use  on  locomotives  because  of  their  intense  draft,  the  hollow  arch 
has  recently  come  into  prominence.  Its  principle  is  simply  that  of  a 
conduit  providing  a  passage  for  the  admission  of  heated  air  to  the 


16  BOILER  ACCESSORIES 

firebox  above  the  fire,  in  addition  to  the  air  that  comes  up  through 
the  grate  from  below  in  the  ordinary  way.  Its  object  is  to  keep  the 
supply  of  oxygen  at  all  times  sufficient  in  quantity,  and  at  the  proper 
temperature,  to  insure  a  practically  perfect  combustion  of  the  uncon- 
sumed  carbon  and  hydrocarbon  gases  which  are  ordinarily  wasted  and 
lost  in  the  form  of  black  smoke  pouring  from  the  stack.  It  thus 
insures  an  economy  of  fuel  and  a  proportional  reduction  in  operating 
expense. 

The  problem  of  securing  complete  combustion  of  fuel  on  a  loco- 
motive, is  one  that  presents  peculiar  difficulties.  The  quantity  of 
fuel  to  be  burned  is  so  large,  and  the  firing  space  relatively  so  small, 
that  the.  conditions  usually  are  unfavorable  for  economical  combustion. 
A  ton  of  average  bituminous  coal  contains  about  1,000  pounds  of  pure 
carbon,  700  pounds  of  hydrocarbon  gases,  and  300  pounds  of  non- 
combustible  matter  or  ash.  The  1,700  pounds  01  carbon  and  hydro- 
carbons require  about  300,000  cubic  feet  of  air  for  their  complete 
combustion.  In  the  ordinary  method  of  burning  coal  on  a  loco- 
motive, fully  90  per  cent  of  this  air — or  270,000  cubic  feet  per  ton  of 
fuel  burned — must  be  drawn  up  through  the  grate-bars  and  firebed. 
This  is  practically  impossible  without  forcing  the  draft  to  such  an 
extent  that  the  fire  will  .be  pulled  off  the  grates,  and  more  or  less  of  the 
unburned  coal  carried  away  through  the  flues  and  stack.  The  result 
is  that  the  supply  of  air  actually  used  is,  as  a  general  thing,  insufficient 
for  perfect  combustion,  and  the  combustible  carbon  smoke  and  gases 
pass  out  of  the  stack  without  giving  up  all  of  their  heat  to  the  water 
in  the  boiler.  The  energy  they  contain  is  simply  wasted. 

How,  then,  can  this  be  prevented?  In  other  words,  since  the 
quantity  of  air  that  comes  through  the  grates  is  insufficient,  how  can 
we  get  enough  air  to  the  fuel  without  interfering  with  the  fire?  It 
must  be  let  in  above  the  fire;  but  it  will  not  do  to  admit  cold  air,  which, 
as  every  fireman  knows,  would  act  as  a  damper  on  the  fire,  retarding 
combustion,  and  increasing  rather  than  preventing  smoke  and  loss 
of  energy.  The  air  to  be  admitted  to  the  fire  must  first  be  heated  to 
as  near  the  ignition  point  as  possible. 

This  is  done  by  means  of  the  hollow  arch.  One  of  these  arches 
of  the  "Wade-Nicholson"  type,  installed  on  a  locomotive,  is  illustrated 
in  Fig.  15,  the  method  of  operation  being  clearly  indicated.  The 
device  may  be  installed  at  both  back  and  front  ends  of  the  firebox. 


BOILER  ACCESSORIES 


17 


The  hollow  passage  through  the  arch  leads  directly  through  suitable 
openings  in  the  firebox  sheets,  from  the  outer  air  to  the  combustion 
chamber,  being  deflected  downward  toward  the  fire  at  the  inner  end. 
The  walls  of  the  arch,  being  highly  heated,  impart  their  heat  to  the  cur- 
rent of  air,  which,  as  it 
emerges  into  the  firebox,  is 
practically  at  the  tempera- 
ture of  ignition.  There 
mingling  directly  with  the 
coinbustible  gases,  an  ap- 
proximately perfect  com- 
bust  ion  is  established. 
The  resulting  economy  in 
fuel  is  estimated  to  aver- 
age a  saving  of  at  least  8 
per  cent. 

The  Chicago  &  North- 
western Railway,  has, 
after  severe  test,  adopted 
arches  of  the  above  type 
on  over  200  of  its  locomotives ;  and  its  example  has  been  followed  on 
many  of  the  locomotives  of  the  Santa  Fe,  the  Chicago,  Milwaukee  & 
St.  Paul,  the  Pere  Marquette,  the  Duluth  &  Iron  Range,  and  other 
important  railroads  in  this  country.  In  addition  to  the  saving  in 
fuel,  the  following  advantages  are  claimed  for  the  hollow  arch : 

Being  air-cooled,  its  life  is  two  to  three  times  that  of  the  ordinary  solid 
brick  arch. 

It  does  away  with  tire  smoke  nuisance. 

The  air,  being  heated  before  striking  the  combustible  gases,  unites  with 
them  instantly,  giving  a  brighter,  cleaner,  more  intense  fire,  and  resulting 
in  a  better  steaming  engine. 

The  back  arch  acts  as  a  baffle-sheet,  protecting  the  crown  sheet  and 
upper  flues,  and  gives  a  more  uniform  distribution  of  heat  throughout,  re- 
sulting in  less  leaky  flues  and  a  saving  in  boiler  repairs. 

The  arch  can  be  used  either  with  or  without  water-filled  circulating 
arch  tubes  as  supports. 

Arches  can  readily  be  removed  and  reset,  in^whole  or  in  part,  without 
damage,  to  give  access  to  flues  when  repairs  are  needed. 

Fuel  Economizers.  Many  devices  have  been  employed  whereby 
a  portion  of  the  heat  may  be  extracted  from  the  gases  as  they  pass 


Fig.  15.     Wade-Nicholson  Hollow  Arch  Installed  in 

Locomotive  Boiler.    The  Water-Tube  Supports 

Here  Shown  are  Sometimes  Omitted. 


18 


BOILER  ACCESSORIES 


BOILER  ACCESSORIES 


Id 


from  the  boiler  to  the  uptake.  Most  of  these  consist  of  a  tubular 
arrangement  through  which  the  hot  gases  pass ;  but,  as  these  are  soon 
covered  with  a  thick  deposit  of  soot,  they  quickly  become  inoperative. 
The  "Green"  economizer  (Fig.  16)  solves  this  difficulty  by  means  of 
small  scrapers  which  work  up  and  down  between  Jhe  tubes.  These 
scrapers  are  operated  by  a  small  engine,  and  keep  the  tubes  free  from 
soot.  The  feed-water  is  pumped  through  these  tubes  on  its  way  to 
the  boiler,  and  is  thoroughly  heated.  An  economizer  of  this  sort  will 
extract  40  per  cent  or  more  of  the  heat  from  the  waste  gases,;  but  by 
reducing  the  temperature  of  these  gases,  the  draft  is  somewhat  reduced, 
and  either  the  chimney  must  be  built  higher,  or  a  blower  must,  be 
used. 

Mechanical  Stokers.  The  mechanical  stoker,  which  feeds  coal 
and  tends  fires  by  machinery,  is  coming  more  and  more  into  general  use. 
With  a  good  mechanical  stoker,  one  man  can  tend  several  furnaces 
with  little  labor.  There  are  several  different  types,  and  in  most  of 
them  the  coal  is  fed  into  a  hopper  of  such  size  that  it  need  not  be  often 
filled.  Some  stokers  work  continuously;  others,  only  when  thrown 

into  gear  by  the 

— — 


fireman.  In  the 
"Roney"  stoker 
(Fig.  17),  the 
grate-bars  ex- 
tend across  the 
furnace,  and 
form  a  series  of 
steps  down 
which  the  fuel 
moves.  Each 
grate  bar  is  hung 
on  pivots  at  the 

ends,  and  is  operated  by  a  rocker-bar.  This  rocker-bar  is  driven  by  a 
small  steam  engine,  with  a  slow,  regular  reciprocation  which  causes 
the  grate-bars  .to  tip  so  that  the  coal  of  its  own  weight  slides  from 
one  grate-bar  to  the  next.  Coal  from  a  hopper  falls  onto  a  hori- 
zontal plate,  and  is  fed  into  the  top  of  the  grate  by  a  pusher.  The 
rapidity  with  which  the  fuel  can  be  fed,  is  regulated  by  changing  the' 
stroke  of  the  pusher  and  by  governing  the  speed  of  the  engine.  Ashes 


Fig.  17.    Detail  of  "Honey"  Mechanical  Stoker. 


20  BOILER  ACCESSORIES 


and  clinkers  collect  on  the  dumping-grate  at  the  end  of  the  grate-bars, 
whence  they  can  be  dumped  into  the  ash-pit. 

This  type  of  grate  is  well  adapted  for  smoke  prevention,  for  the 
fresh  fuel  fed  in  at  the  top  is  rapidly  coked,  and  the  volatile  gases  are 
easily  consumed.  The  rapidity  of  feed  should  be  so  regulated  that 
no  unburned  fuel  gets  past  the  dump-grate.  If  the  fire  becomes  too 
thin,  there  will  be  a  loss  of  efficiency  due  to  the  excess  of  air  which 
passes  through  the  burning  fuel.  It  is  easy  to  detect  the  loss  from 
too  much  fuel,  but  not  so  easy  if  there  is  too  little  fuel. 

All  mechanical  stokers  in  which  the  movable  parts  are  inside  the 
furnaces,  are  likely  to  get  out  of  order  because  of  the  heat  and  dirt. 

Fusible  Plugs.  Fusible  plugs  are  usually  inserted  in  the  top 
sheet  or  crown  sheet  of  boilers,  as  a  safeguard  against  collapse  of  the 
furnace  crown  should  the  water  in  any  way  be  drawn  out  of  the  boiler 
while  the  fire  is  burning.  These  plugs  consist  of  a  core  composed  of 
an  alloy  of  tin,  lead,  and  bismuth,  with  a  covering  of  brass  or  cast 
iron.  The  United  States  inspection  law  requires  at  least  one  fusible 
plug  to  be  put  in  every  marine  boiler,,  with  the  exception  of  water- 
tube  boilers,  the  plug  to  be  made  of  a  bronze  casing  filled  with  good- 
quality  "Banca"  tin  from  end  to  end.  While  this  plug  is  kept -at  a 
comparatively  low  temperature  by  water  on  one  side,  the  fire  on  the 
other  side  will  not  melt  it;  but  when  the  water-level  becomes  low 
enough  to  leave  one  end  of  the  plug  uncovered,  the  alloy  core  of  the 
plug,  having  a  comparatively  low  melting  point,  will  fuse,  thus  running 
out  of  its  casing,  relieving  the  pressure  in  the  boiler,  and  allowing  the 
excess  of  steam  to  extinguish  the  fire,  which  otherwise  would  be  likely 
to  destroy  the  crown  sheet. 

Fusible  plugs  are  frequently  unreliable.  Sometimes  they  will 
blow  out  when  there  is  no  apparent  cause,  and  sometimes  remain 
intact  when  the  plates  have  become  overheated.  If  a  coating  of  hard 
scale  is  allowed  to  accumulate  over  the  plug,  it  may  stand  consider- 
able  pressure,  even  after  the  core  has  become  melted.  To  provide 
against  this,  the  plug  should  be  replaced  frequently.  If  allowed  to 
remain  in  the  boiler  for  any  length  of  time,  the  composition  of  the 
alloy  is  likely  to  change,  the  plug  thus  becoming  more  or  less  unre- 
liable. 

Figs.  18  and  19  illustrate  the  ordinary  plug.  It  should  be  so 
made  that,  when  screwed  into  the  crown  sheet,  it  will  project  1^  or 


BOTLER  ACCESSORIES 


21 


2  inches  above  the  plates,  so  that  when  the  alloy  melts  there  will  be  a 
sufficient  depth  of  water  over  the  crown  sheet  to  prevent  injury  from 
heat. 

Sometimes  the  core  is  covered  with  a  thin  copper  cap,  as  shown 


Fig.  18.  Fusible  Plug.    At  Right  is  Sectional  View  of  Plug  Attached  to  Crown 
Sheet  of  Boiler,  to  Give  Automatic  Warning  in  Case  of 
Overheating  of  Plates. 

in  Fig.  18,  which  protects  the  alloy  from  contact  with  the  water,  thus 
preventing  a  chemical  change  and  the  formation  of  scale.  It  does 
not  necessarily  follow  that  a  hole  i  inch  or  f  inch  in  diameter  will 


Fig.  19.    Illustrating  Action  of  Fusible  Plug  Attached  to  Crown  Sheet. 

liberate  steam  fast  enough  to  prevent  excess  of  pressure.     If  a  small 
quantity  of  steam  is  introduced  into  the  firebox,  it  may  have  the 


22  60ILER  ACCESSORIES 

. — . , , — -..,^~ 

effect  of  brightening  the  fire  and  increasing  the  heat  of  combustion, 
owing  to  the  formation  of  water  gas  as  the  steam  mingles  with  the 
burning  coal.  The  steam,  moreover,  might  have  the  effect  of  inducing 
additional  draft.  If,  however,  the  quantity  of  escaping  steam  and 
water  is  considerable,  combustion  will  be  retarded,  and  the  fire  will 
be  partially  extinguished.  It  will  operate  to  warn  the  fireman  of 
what  has  happened;  and  if  the  escape  of  steam  is  not  too  rapid,  he 
may  throw  on  wet  ashes  and  deaden  the  fire. 

NATURAL  AND  FORCED  DRAFTS 

The  draft  in  a  chimney  is  caused  by  the  difference  in  weight 
between  the  volume  of  heated  gases  inside  and^the  outside  air.  This 
being  so,  it  is  apparent  that  the  taller  the  chimney,  the  greater  this 
difference  will  be.  The  force  or  intensity  of  a  draft  is  increased,  and 
additional  draft  is  induced,  by  the  force  of  the  wind  as  it  whistles  by 


Fig.  20.    "Eames  Differential"  Draft-Gauge. 

the  chimney  top.  The  intensity  may  at  any  time  be  measured  by  a 
draft-gauge.  The  most  satisfactory  instrument  of  this  sort  is  the 
"Eames  Differential"  draft-gauge,  shown  in  Fig.  20.  The  tube  is 
filled  with  a  special  non-drying,  non-evaporating  oil  of  known  specific 
gravity.  The  incline  and  diameter  of  the  tube  are  so  proportioned 
that  the  readings  are  equivalent  to  inches  of  water,  in  which  terms 
the  draft  is  invariably  measured. 

Other  things  being  equal,  the  rate  of  combustion  depends  upon 
the  height  of  the  chimney.  A  chimney  20  to  25  feet  in  height  will 
cause  a  draft  sufficient  to  burn  about  8  Ibs.  of  coal  per  square  foot  of 
grate  area  per  hour.  If  the  height  is  increased  to  about  100  feet, 
the  rate  of  combustion  will  be  increased  to  approximately  15  Ibs.  per 
square  foot;  and  to  burn  25  Ibs.,  the  chimney  should  be  about  175 
feet  high.  This  is  measured  above  the  grate  of  the  boiler.  For  good 
bituminous  or  anthracite  coal,  the  chimney  must  be  higher  than  for 


BOILER  ACCESSORIES  23 

wood,  if  the  same  rate  of  combustion  is  desired.  If  the  boiler  has 
small  or  winding  passages,  the  chimney  must  be  higher  to  produce 
the  same  effective  draft.  High  chimneys  are  costly;  and  it  is  fre- 
quently the  practice  to  build  two  or  three  small  chimneys  in  place  of 
the  big  one,  and  to  supplement  them  with  some  form  of  forced  draft. 

By  means  of  forced  draft,  the  rate  of  fuel  combustion  can  be 
increased  under  favorable  conditions  to  100  Ibs.  of  coal  per  square 
foot  of  grate  surface  per  hour.  This,  of  course,  greatly  increases  the 
power  of  the  plant,  but  is  likely  to  injure  the  boiler,  and  is  uneconomi- 
cal under  most  conditions.  There  are  three  systems  of  forced  draft 
in  common  use : 

1.     The  closed  stoke-hold,  as  used  in  marine  work; 

2o    The  closed  ash-pit-, 

3.    The  induced  draft. 

Closed  Stoke-Hold.  One  of  the  most  common  forms  of  forced 
draft,  especially  as  used  on  warships,  is  obtained  by  closing  the  stoke- 
holds and  blowing  a  fresh  supply  of  air  into  the  fire-room.  This  gives 
an  exceedingly  good  ventilation  and  keeps  the  fire-room  in  good  con- 
dition; but  its  chief  objection  is  that  when  the  furnace  doors  are 
opened  there  is  a  tremendous  indraft  of  cold  air,  which  tends  to  lower 
the  efficiency  of  the  boiler.  If  this  system  is  employed,  the  bulk- 
heads adjacent  to  the  boiler-room  must  be  provided  with  double  doors, 
forming  an  air-lock  between.  By  opening  only  one  door  at  a  time,  the 
pressure  in  the  fire-room  is  not  lost.  This  system  seems  to  possess 
but  one  distinct  advantage,  and  that  is  coolness  and  therefore  comfort 
for  the  firemen;  but  the  disadvantage  of  the  inrush  of  air  to  the 
furnaces  when  firing,  is  sufficient,  in  some  cases,  to  make  the  system 
questionable. 

Closed  Ash-Pit.  The  essential  features  of  forced  draft  by  this 
method  consist  merely  in  closing  the  ash-pit  tight,  and  blowing  the  air 
directly  under  the  grate.  When  the  fires  are  cleaned,  the  draft,  of 
course,  must  be  shut  off;  otherwise  the  flames  will  be  blown  out  into 
the  fire-room.  The  fire-room,  under  this  system,  is  likely  to  be 
hotter  than  by  the  other  method ;  but  this  system  would  seem  to  be  the 
better  from  a  mechanical  point  of  view. 

There  are  several  patented  devices  in  connection  with  the  forced 
draft,  of  which  the  "Howden"  and  the  "Ellis  and  Eaves"  systems 
may  be  specially  mentioned.  It  may  be  worth  while  to  note  that  if  fuel- 


24  BOILER  ACCESSORIES 

oil  is  burned,  any  one  of  these  systems  of  forced  draft  will  work  better 
than  with  coal,  for  the  fire  can  be  tended  without  opening  the  fire- 
doors. 

Induced  Draft.  Perhaps  the  most  common  example  of  induced 
draft  is  to  be  found  in  the  locomotive,  where  the  exhaust  steam  is 
turned  into  the  smokestack.  The  rush  of  this  steam  up  the  stack, 
by  carrying  a  large  volume  of  air  with  it,  induces  a  tremendous  draft. 
Induced  draft  may  also  be  obtained  in  stationary  and  marine  plants 
by  placing  a  blower  in  the  chimney  or  stack.  In  marine  work,  of 
course,  induced  draft  by  exhaust  steam  is  out  of  the  question.  When 
a  blower  is  placed  in  the  smokestack,  an  economizer  should  be  used, 
so  that  the  gases  may  be  cooled  before  they  reach  the  blower.  The 
draft  obtained  on  locomotives  is  frequently  equivalent  to  a  column 
of  five  or  six  inches  of  water;  while  a  forced  draft  of  two  inches  is 
usually  considered  large,  except  for  torpedo-boats,  which  may  have 
as  strong  a  draft  as  a  locomotive  has. 

Howden  System.  The  Howden  system  of  forced  draft  with 
closed  ash-pit  has  been  used  to  a  considerable  extent  in  both  mer- 
cantile and  naval  service.  The  air  supplied  to  the  ash-pit  is  first 
heated  by  passing  through  a  heater  in  the  uptake.  Waste  gases  pass 
through  tubes;  and  the  air,  passing  among  them  before  entering  the 
furnace,  is  heated  to  a  high  temperature.  A  consumption  of  60  Ibs. 
of  coal  per  square  foot  of  grate  is  easily  obtained  with  this  system; 
and  care  must  be  taken  that  the  fire  is  not  forced  too  hard,  as  there  is 
more  danger  of  burning^  out  the  grate  than  if  the  air-supply  is  not 
heated. 

Ellis  and  Eaves  System.  Heating  the  air  does  not  necessitate  its 
being  forced  into  the  closed  ash-pit,  for  it  is  quite  feasible  to  heat  the 
air  in  connection  with  draft  induced  by  an  exhaust  fan  at  the  base  of 
the  funnel.  Such  is  the  Ellis  and  Eaves  system.  This  system  was 
first  tried  in  the  boiler  shops  at  the  works  of  the  John  Brown  Company, 
in  Sheffield,  England,  and  was  later  adopted  on  many  vessels.  The 
Ellis  and  Eaves  heater  is  fixed  on  top  of  the  boilers,  and  is  divided 
into  two  parts  separated  at  the  front  by  a  smoke-box  and  at  the  back 
by  a  funnel.  The  hot  gases,  therefore — which  pass  outside  the  tubes — 
have  to  take  a  somewhat  circuitous  course;  while  the  passage  of  the 
air  to  be  heated,  on  the  contrary,  takes  a  direct  course.  The  dis- 
tribution of  air  to  the  ash-pit  is  similar  to  that  of  the  Howden  system. 


BOILER .  ACCESSORIES  25 


The  advantages  of  this  system  lie  in  the  general  convenience  of  the 
induced  draft  and  the  absence  of  jets  of  hot  air  shooting  out  into 
the  boiler-room.  The  draft  need  not  be  shut  off  when  stoking  the 
fires,  unless  it  is  desired  to  prevent  the  inrush  of  air  already  referred  to 
under  the  general  discussion  of  "closed  stoke-holds."  The  air  in  the 
fire-room  being  of  a  relatively  higher  temperature  than  would  obtain 
with  closed  stoke-holds,  and  the  quantity  being  much  less,  this  objec- 
tion has  no  great  weight.  With  the  Howden  system  it  is  necessary 
that  the  doors  should  be  tight;  otherwise  hot  air  will  be  blown  out 
into  the  fire-room.  With  this  system  a  few  leaks  are  of  no  conse- 
quence, and  the  fire-room  will  be  somewhat  cooler  than  with  the 
Howden  System.  The  objections  to  the  Ellis  and  Eaves  system  are 
these  inherent  in  any  system  of  draft  induced  by  a  fan — that  is  to  say, 
a  poor  efficiency  of  the  fan  working  in  heated  gases,  and  lost  work  in 
drawing  air  through  tortuous  passages. 

Steam  Jets.  Steam  jets  may  be  used  for  inducing  a  draft.  They 
may  be  placed  either  in  the  smokestack,  or  below  or  above  the  grate; 
but  in  general  they  are  not  so  economical  as  a  fan  used  for  the  same 
purpose.  In  locomotives  and  fire-engines,  where  the  exhaust  steam 
is  at  high  pressure,  an  intense  draft  may  be  induced  by  exhausting 
this  up  the  smokestack.  In  both  these  cases,  the  saving  of  weight 
due  to  the  use  of  a  small  boiler  running  at  high  tension,  is  of  greater 
practical  importance  than  the  economy  of  fuel ;  and  for  such  purposes 
this  arrangement  is  entirely  satisfactory. 

A  steam  jet  may  be  used  directly  in  the  furnace,  either  above  or 
below  the  grate.  The  steam  enters  through  a  small  pipe,  and  ex- 
pands through  a  nozzle  surrounded  by  an  annular,  funnel-shaped 
tube.  The  escape  of  steam  from  the  inner  nozzle  draws  in  a  large 
volume  of  air  through  the  outer  tube,  and  produces  an  intense  draft. 
If  steam  is  blown  into  the  ash-pit  in  this  manner,  it  forms  a  sort  of 
producer  gas  by  mingling  with  the  incandescent  fuel,  and  materially 
aids  in  the  combustion  of  cheap  and  apparently  worthless  fuel.  Al- 
most as  poor  fuel  can  be  successfully  used  with  this  arrangement  as 
can  be  used  in  the  grates  of  the  down-draft  furnaces.  Such  arrange- 
ments have  given  excellent  satisfaction,  and  the  production  of  smoke 
is  materially  lessened. 

Some  tests  made  in  the  French  Navy  some  years  ago,  showed 
that,  with  the  use  of  the  steam  jet  above  the  grate,  the  coal  con- 


26 


BOILER  ACCESSORIES 


sumption  per  square  foot  of  grate  area  could  readily  be  doubled; 
but  this  result  would  be  attained  at  the  expense  of  fuel  economy; 
for,  while  with  natural  draft  one  pound  of  coal  produced  approxi- 
mately eight  pounds  of  steam  which  could  be  used  by  the  engine, 
with  a  steam  jet  less  than  6f  pounds  of  steam  per  pound  of  coal  was 
available  for  like  purposes.  The  total  evaporation  per  pound  of  fuel 
was  approximately  the  same  in  each  case,  the  difference  being  the 
quantity  of  steam  used  in  the  jet.  If  a  steam  jet  is  used  on  board 
ship,  it  consumes  a  considerable  amount  of  fresh  water,  which  must 
be  replaced  by  evaporators,  or  by  the  use  of  salt 
water,  which  is  decidedly  objectionable. 

TUBE=CLEANERS 

To  secure  the  best  results  from  a  boiler,  the 
tubes  should  be  kept  thoroughly  clean.  The  collec- 
tion of  soot  on  the  tubes  is  .as  detrimental  to 
economy  as  the  formation  of  boiler  scale.  The  soot 
may  be  removed  by  the  insertion  of  brushes  when 
the  boiler  is  'not  under  steam,  or  the  tubes  may 
be  blown  out  with  a  steam  jet  designed  for  this 
purpose.  Fig.  21  illustrates  forms  of  tube-cleaners, 
of  which  there  are  numerous  types  on  the  market. 
The  type  shown  at  B  is  de- 
signed for  use  with  a  steam 
jet.  In  the  case  of  oil-burn- 
ing locomotives,   the  tubes 
are  usually  cleaned  with  the 
aid  of  a  sand-blast. 


A  B   . 

Fig.  21.    Types  of  Tube-Cleaners. 


TUBE-STOPPERS 


It  frequently  happens, 
when  tubular  boilers  are  under  pressure,  that  leaks  occur  in  the 
tubes  through  pitting,  defective  welding,  or  the  development  of 
cracks.  Formerly,  when  this  occurred,  the  fire  was  drawn,  and  thu 
ends  of  the  tube  plugged  with  hardwood  bungs  driven  hard  home  or 
with  iron  plugs  calked  in.  With  high  pressures,  such  procedure  is 
impossible.  Tube-stoppers  used  for  high  pressure  are  joined  to- 
gether by  a  tie-bar  of  some  sort.  They  are  usually  wedge-shaped ;  and 


BOILER  ACCESSORIES 


27 


the  tie-rod,  passing  through  the  stopper  at  one  end,  with  a  plug  at  the 
other  end,  can  be  screwed  hard  up. 

The  simplest  form  of  stopper  has  to  be  inserted  from  the  rear,  and 
necessitates  drawing  the  fire ;  but  Fig.  22  illustrates  a  stopper  which 
can  be  inserted  without  drawing  the  fire.  At  the  end  of  the  rod  is 
hinged  a  folding  bung,  which  can  be  passed  through  the  tube  and 


Fig.  22.    Tube-Stopper  Designed  for  Insertion  without  Drawing  Fire. 

which  opens  out  in  the  combustion  chamber  before  being  pulled  into 
position.  At  the  smoke-box  end  of  the  boiler,  an  india-rubber 
washer,  pressed  between  two  pieces  of  metal,  affords  temporary 
protection  while  the  plug  is  being  put  in  position.  The  stopper  can 
then  be  screwed  up  tightly  with  a  handle  provided  for  that  purpose. 
Fig.  23  illustrates  another  arrangement  wrhich  can  be  inserted 
in  the  leaky  tube  without  drawing  the  fire.  The  ends,  being  in  the 


28 


BOILER  ACCESSORIES 


form  of  stuffing  glands,  press  an  asbestos  packing  hard  against  the 
side  of  the  tube. 


Another  Type  of  Tube-Stopper  Used  without  Drawing  Fire.    As  the  Parts  are 
Screwed  Up,  the  Asbestos  Packing  is  Driven  Hard  against  Side  ef  Tube. 

MANHOLES  AND  HAN  DHOLES 

A  manhole  allows  access  to  the  boiler  for  cleaning  and  repairs, 
It  is  usually  elliptical  in  form  and  large  enough  to  admit  a  maii. 

About  16  inches  for  the  major  axis,  and 
12  for  the  minor  axis,  is  a  good  size. 
The  manhole  is  closed  by  a  plate  or 
cover  made  of  cast  or  wrought  iron. 
This  plate  is  held  to  the  seat  by  a  yoke 
or  yokes,  and  bolts.  Fig.  24  shows  one 
form,  Y  being  the  yoke,  L  the  cover, 
and'-ZV  the  bolt.  The  joint  between 
the  cover  and  the  shell  is  made  steam 
tight  by  packing. 

The  strength  of  the  boiler  should 
always  remain  unimpaired;  so,  when- 
ever a  large  hole  is  cut  in  the  plate, 
the  edge  should  be  strengthened,  for 

Manhole  cover.  t}ie  tension  is  concentrated  there,  and 

the  plates  are,  moreover,  likely  to  become  weak  by  corrosion.  The 
strain  put  upon  the  plate  by  screwing  up  the  cover,  if  no  packing 
is  used,  is  considerable,  especially  if  a  piece  of  scale  gets  between  the 
faces  and  the  joint  is  then  made  tight. 


j 

L 

Fig. 


It* 


«  £  g 

+3  ^ 

ir 


Q  s 
w  -3 
ou.  ,3 

Pu 

p 
or 

w 


BOILER  ACCESSORIES 


29 


Fig.  25  shows  the  section  of  a  strong  and  simple  manhole.  The 
edge  of  the  plate  is  strengthened  by  a  broad  ring  of  steel,  which  is 
flanged  and  riveted  to  the  shell,  its  edge  forming  the  seat.  The  cover 
as  shown  in  the  figure  is  shaped  for  strength.  The  edge  of  the  ring 
which  forms  the  seat,  and  the  cover,  are  machined  to  make  a  tight  joint 
without  packing.  The  strengthening  ring  should  be  at  least  f  inch 
thick  and  4  inches  wide,  that  the  rivet-holes  may  not  be  too  near  the 
edge. 

Handholes  and  mudkoles  are  more  commonly  placed  in  boilers, 
which  are  so  constructed  that  a  man  cannot  enter — in  a  vertical  boiler, 
for  example.  They  are  used  to  some  extent  in  other  boilers;  in 
horizontal  return-tube  boilers  there  is  usually  a  handhole  in  each  end, 


Fig.  25.    Section  of  a  Strong  but  Simple  Type  of  Manhole. 

near  the  bottom.  Handholes  are  very  convenient  to  admit  hose  for 
washing  out  the  boiler,  also  for  removing  scale  and  sediment.  Hand- 
holes  are  similar  to  manholes  in  construction,  but  require  only  one 
yoke  and  one  bolt  to  keep  them  in  place.  Mudholes  should  be  pro- 
vided in  order  that  the  sediment  and  detached  scale  can  be  removed 
without  lifting  the  accumulated  mass  to  the  top  manhole.  Mudholes 
and  handholes  greatly  facilitate  cleaning  the  fire-box  water-leg  of 
locomotive  and  small  vertical,  boilers. 

STEAM  AND  VACUUM  GAUGES 

The  steam  pressure  in  the  boiler  is  measured  in  pounds  per 
square  inch.  When  we  say  the  boiler  is  working  or  steaming  at  80 
pounds'  pressure,  we  mean  that  the  gauge  pressure  is  80  pounds;  that 
is,  the  pressure  in  the  boiler  is  80  pounds  above  atmospheric  pressure. 
It  could  be  measured  by  a  water  or  mercury  column;  but,  as  these 
would  need  to  be  very  high  to  measure  the  pressures  used  at  the  present 
day,  they  are  not  practicable,  and  so  a  spring-pressure  gauge  is  used 
instead. 

The  dial  gauge,  now  used  almost  universally,  was  invented  by 
M.  Bourdon.  It  is  designed  in  accordance  with  the  principle  that  a 


30 


BOILER  ACCESSORIES 


flattened,  curved  tube  closed  at  one  end   tends   to   become   straight 
when  subjected  to  internal  pressure. 

The  tube,  which  is  usually  oval  in  section,  is  bent  into  the  arc 
of  a  circle  as  shown  in  Fig.  26.  One  end  is  fixed,  and  is  in  com- 
munication with  the  boiler.  The  other 
is  closed  and  free  to  move.  By  means 
of  levers,  a  curved  rack,  and  a  pinion, 
the  motion  of  the  free  end  is  multiplied 
and  indicated  by  a  needle,  which  is 
attached  to  the  pinion.  The  needle 
moves  over  a  dial  which  is  graduated 
to  agree  with  a  mercury  column,  or 
with  a  standard  gauge.  The  back-lash 
of  the  levers  is  taken  up  by  a  hair 
spring.  Fig.  27  shows  the  interior  and 
face  of  a  Bourdon  steam  gauge  manu- 
factured by  the  American  Steam  Gauge 
Company. 

Fig.  28  shows  the  exterior  and  interior  of  a  steam  gauge  with 
a  light  tube  for  low  pressures;  the  face  of  the  dial  is  graduated  corre- 
sponding to  the  mercury  column.  The  only  difference  between  this 
gauge  and  the  vacuum  gauge,  is  that  in  the  latter  the  curved  tube  is 


Fig.  26.    Steam-Filled  Curved  Tube 
Indicating  Pressure  in  Bour- 
don Steam  Gauge. 


Fig.  27.    Interior  Mechanism,  and  Dial,  of  "Lane"  Type  of  Steam  Gauge. 

turned  in  the  opposite  direction  so  that  the  needle  will  move  clockwise 
with  a  decrease  of  pressure. 


BOILER  ACCESSORIES 


31 


On  account  of  the  jarring,  the  gauge  for  locomotives  must  be 
very  strong.  To  prevent  excessive  vibration  of  the  needle,  two  short, 
stiff er  springs  are  used,  as  shown  in  Fig.  29. 


Fig.  28.    Interior  Mechanism,  and  Dial,  of  Low-Pressure  Steam  Gauge. 

Sometimes  two  pressure  gauges  are  fitted  to  a  boiler,  one  indicating 
the  working  pressure,  and  the  other  graduated  to  about  twice  the  work- 
ing pressure.  The  latter  is  useful  in  testing  the  boiler  under  water 
pressure,  and  also  serves  as  a  check  on  the  other.  The  pipe  which  con- 
nects the  pressure  gauge  to  the  boiler  should  have  bends  in  it  near  the 
gauge.  These  bends — or,  better,  a  coil  pipe,  as  shown  in  Fig.  30 — 


Fig.  29.    Steam  Gauge  for  Use  ou  Locomotives.    Excessive  Vibration  of  Needle 
Prevented  by  Use  of  Two  Short,  Stiff  Springs. 

are  filled  with  water,  which  transmits  pressure  and  keeps  the  spring  at 
a  nearly  constant  low  temperature.     Gauges  should  be  placed  where 


32 


BOILER  ACCESSORIES 


the  water  in  the  coiled  pipe  will  not  freeze;  also,  the  gauge  should 
not  be  exposed  to  strong  heat.     In  order  that  the  gauge  may  be 


Fig.  30.    Water-  Filled  Coil  Pipe  for  Connection  to  Steam  Gauge.    The  Water 
Transmits  Pressure  and  Regulates  Temperature. 

removed  from  the  boiler  for  examination,  repairs,  or  calibration, 
when  the  boiler  is  under  pressure,  the  connection  should  be  provided 
with  stop-cocks. 

In  a  battery  of  boilers,  each  should  have  its  pressure  gauge,  which 
should  be  connected  directly  to  the  boiler,  not  to  the  steam  pipe. 

WATER  GAUGES 

It  is  of  great  importance  that  the  level  of  the  water  in  the  boiler 
can  easily  be  ascertained  at  all  times.     Should  the  level  be  too  low, 

there  is  danger 
o  f  overheating 
the  furnace  plates 
or  tubes.  If  it  is 
too  high,  there  is 
likely  to  be  an 
undue  amount  of 
The 


prmng. 

water-level  is 
usually  indicated 
by  gauge-cocks 
or  try-cocks  or 
watergauge- 
glasses.  Some- 
times a  float  is 
provided,  which 
is  connected  to  a  small  whistle,  and  if  the  water-level  falls  below  a 


Fig.  31.    Ordinary  Form  of  Try-Cock  for  Determining  Water- 
Level  in  Boiler. 


BOILER  ACCESSORIES 


33 


Fig.  32.    Try-Cock  Operated  by  Means  of  Lever. 


certain  point,  an  alarm  is  sounded.     Such  a  device  can  readily  be 

used  in  conjunction  with  the  ordinary  water-gauge. 

Try-Cocks.    Try-cocks   are  very  generally  used.     They  are  of 

widely  different 
forms,  and  may 
be  either  like  the 
general  type 
shown  in  Fig.  31, 
which  is  the  ordi- 
nary 1  o  c  o  m  o- 
tive  form,  con- 
structed in  two 

parts  so"  that  they  can  be  separated  for  the  purpose  of  repacking 

without  detachment  from  the  boiler;   or 

they  may  be  of  the  lever  type  shown  in 

Fig.  32.     There  are  usually  three  cocks, 

one  at  the  highest  desired  water-level,  one 

at  the  lowest,  and  one  midway.       More 

cocks  may,  of  course,  be  used  if  desired. 

The    water-level   can   be  determined  by 

opening  the  cocks  in  succession  and  ob- 
serving whether  dry  steam  or  hot  water 

flows  out.      If  the  boiler  is  encased  in 

brickwork,  as  is  customary  for  externally- 
fired  boilers,  the  gauge-cocks  are  placed 

outside  the  brickwork,  and  are  connected 

to   the   boiler  by  nipples  of  the  proper 

length. 

Qauge-Glasses.      In   order   that  the 

fireman  may  know  the  water-level  without 

trying  the  cocks,  a  water  gauge-glass  is 

used.      It  consists  of  a  strong  glass  tube 

about  one  foot  in  length,  having  the  ends 

connected  to  the  boiler  by  suitable  fittings. 
As  both  ends  of  the  tube  are  in  com- 
munication with  the  boiler,  the  water-level 

in  the  glass  will  be  the  same  as  in  the 

boiler,  and  is  always  in  sight.    Fig.  33  shows  a  good  form  of  gauge- 


Fig.  33.    A  Good  Type  of  Water 
Gauge-Glass. 


34 


BOILER  ACCESSORIES 


glass.  The  glass  is  protected  by  rods  which  are  parallel  to  it.  As 
the  glass  frequently  needs  cleaning,  repacking,  or  renewing,  cocks 
are  provided  for  shutting  off  communication  with  the  boiler.  A 
drain-cock  is  also  placed  at  the  lower  end  to  empty  the  glass  when  the 
attendant  wishes  to  ascertain  whether  the  glass  is  working  properly 
or  not.  The  drain-cock  is  often  provided  with  a  drain-pipe.  The 
steam  and  water  passages  should  be  at  least  one  half-inch  in  internal 
diameter. 

The  glass  is  likely  to  break  because  of  accident  or  of  changes  in 
temperature.  To  prevent  serious  injury  to  the  fireman  and  loss  of 

water  as  a  result  of  the 
breaking  of  the  gauge- 
glass,  automatic  valves 
may  be  placed  in  the 
passages.  In  Fig.  34 
the  ball-valve  is  shown 
in  detail.  If  the  glass 
breaks,  the  pressure  of 
the  steam  drives  the 
ball  outward,  filling 
the  conical  passage. 
When  a  new  glass  is 
put  in,  the  balls  are 
forced  back  by  slowly 
screwing  in  the  stems. 
This,  like  other  safety 
devices,  is  very  likely 
not  to  work  when  it 
should. 

In  boilers  where  the  steam  space  is  small,  as  in  locomotives,  the 
allowable  variation  of  water-level  is  slight;  but  the  greater  care  with 
which  the  glass  is  watched  makes  up  for  the  small  margin  of  safety. 
If  dirty  water  is  used,  or  if  the  water  foams,  the  level  in  the  glass  will 
be  unsteady  and  unreliable,  since  dirt  clogs  the  passages,  unless  they 
are  large,  and  the  foaming  causes  a  fluctuation  of  the  water-level.  A 
small  pipe  connecting  with  the  steam  space  where  no  ebullition  occurs, 
will  insure  a  steadier  water-level.  If  the  steam  and  water  connection* 
are  long,  the  pipes  should  be  made  large. 


Fig.  34.    Automatically  Acting  Ball- Valve  to  Prevent 

Injury  to  Workmen  and  Loss  of  Water  on 

Breaking  of  Gauge-Glass. 


BOILER  ACCESSORIES 


35 


The  chief  objection  to  the  gauge-glass — namely,  its  breaking — 
may  be  to  some  extent  overcome  by  attaching  the  gauge-glass  to  a 
gauge-column,  which  is  usually  made  of  brass  and  stands  quite  clear 


To  Bo^er 


-To  Boiler 


Pig.  35.    Ordinary  Water  Gauge-Glass  Supplemented  (at  right)  by  "Klinger 
Patent"  Gauge-Glass. 

of  the  boiler  itself.  In  such  an  arrangement  as  this,  the  temperature 
in  the  gauge-glass  cannot  vary  so  widely  as  if  it  were  attached  directly 
to  the  boiler.  The  "Klinger  Patent"  water  gauge-glass  is  not  easily 
broken,  and  possesses  many  advantages  over  the  common  glass. 
Fig.  35  illustrates  both  these  devices. 

The  water  gauge  is  not  absolutely  reliable,  for  the  water  in  the 
gauge,  being  cooler  than  that  in  the  boiler,  may  not  indicate  the  true 
level,  and  the  small  passages  leading  to  it  may  become  choked  with 


36 


BOILER  ACCESSORIES 


sediment.     If  the  gauge-glass  is  frequently  blown  out  by  the  engineer 
and  kept  clean,  this  difficulty  will  be  reduced  to  a  minimum. 

VALVES 

Of  all  boiler  accessories,  perhaps  the  most  important  are  the 
cocks  and  valves  by  means  of  which  the  flow  of  steam  or  water  may 
be  shut  off  completely  or  partially.  The  valve  operates  by  moving 
a  disc  across  the  pipe  in  a  transverse  direction,  or  by  bringing  a  cap 


Fig.  36.    Ordinary  "Competition"  Type  of 
Globe  Valve. 


Fig.  37.    Globe  Valve  with  Detachable 

Cap  and  Removable  Interior  Disc 

of  Comparatively  Soft  Material 

to  Insure  Tightness. 


tight  upon  the  seat  in  a  fore-and-aft  direction.  A  cock  consists  of  a 
block  inserted  in  the  passageway,  with  an  opening  cut  through  in  one 
direction.  When  the  handle  of  the  cock  is  in  line  of  the  pipe,  the 
opening  allows  the  steam  to  pass  through;  but  if  turned  crosswise,  the 
opening  is  closed. 

The  Globe  Valve.  The  valve  shown  in  Fig.  36  gets  its  name  from 
the  globular  shape  of  the  casing  which  encloses  the  valve.  Extending 
across  this  whole  casing  is  a  substantial  diaphragm,  the  central  portion 


BOILER  ACCESSORIES 


37 


of  which  is  in  a  plane  parallel  with  the  length  of  the  pipe.  The  open- 
ing is  cut  in  this  portion,  horizontal  in  the  figure,  through  which  steam 
or  other  fluid  may  pass  when  the  valve  is  opened.  When  the  valve  is 
closed,  a  cap  is  forced  down  to  close  its  opening.  The  rim  around 
the  opening  is  known  as  the  valve-seat.  The  valve-cap  is  operated  by 
a  spindle,  which  passes  through  the  bonnet  of  the  valve  and  is  mounted 
at  the  upper  end  by  a  small  wheel  or  handle.  To  prevent  the  escape 
of  steam  around  this  spindle,  a  stuffing-box  is  provided.  The  valve- 
cap  may  or  may  not  rotate  as  the  spindle  turns;  usually  it  does  not. 
The  valve  shown  in  Fig.  36  is  the  ordi- 
nary globe  valve  known  to  the  trade  as 
the  "Competition"  valve.  It  is  the 
cheapest  valve  of  the  type,  and  is  not 
satisfactory  where  absolutely  tight  work 
is  required.  If  the  cap  becomes  scored, 
the  valve  will  leak  and  is  then  worthless. 

A  valve  shown  in  Fig.  37  has  a 
detachable  valve-cap;  and  instead  of 
relying  for  tightness  upon  the  valve 
and  seat  coming  together,  metal  to 
metal,  a  removable  disc  is  provided, 
which  being  softer  than  the  metal  valve- 
seat,  easily  takes  up  the  wear,  and  the 
valve  not  only  can  be  closed  tighter, 
but  if  anything  happens  so  that  the 
tightness  of  the  valve  is  impaired,  the 
valve-cap  can  be  replaced  by  another 
at  a  trifling  expense.  In  the  cheaper 
valve,  when  the  cap  is  scored,  the  valve 
is  worthless.  The  valve-seat  sometimes  has  a  slight  bevel,  the  valve- 
cap  being  shaped  like  the  frustum  of  a  cone. 

It  is  impossible  to  close  a  valve  tightly  if  the  slightest  particle 
of  scale  or  grit  gets  between  the  disc  and  the  seat.  If  this  happens, 
the  valve-seat  is  likely  to  become  scored  so  that  it  does  not  hold  tight; 
but  it  may  be  reground,  and  if  the  valve  disc  itself  is  damaged,  it  can 
readily  be  replaced. 

Angle  Valves.  An  angle  valve,  shown  in  Fig.  38,  is  constructed 
in  a  similar  manner  to  the  ordinary  globe  valve,  and  is  sometimes 


Fig. 


Angle  Valve  of  Oi-dinary 
Globe  Pattern. 


38 


BOILER  ACCESSORIES 


used  in  place  of  the  straightway  valve  and  an  elbow.  Both  these 
styles  of  valve  should  be  so  placed  in  the  steam  pipe  that  the  entering 
steam  comes  beneath  the  valve-seat.  If  this  is  done,  the  valve-stem 
may  easily  be  repacked  simply  by  closing  the  valve.  If  the  steam 
enters  in  the  opposite  direction,  a  leaky  valve-stem  cannot  be  packed, 

as  loosening  the  stuffing-box  would  per- 
mit the  escape  of  the  steam. 

The  Gate  Valve.  The  gate  or 
straightway  valve  gives  a  straight  pas- 
sage through  the  pipe,  and,  when  open, 
.offers  very  little  resistance  to  flow.  The 
globe  valve,  of  course,  offers  much  re- 
sistance, because  the  fluid  has  to  change 
its  direction  of  flow  completely. 

There  are  two  forms  of  gate  valve — 
one  with  wedge-shaped  sides,  and  the 
other  having  the  valve  sides  parallel. 
Fig.  39  shows  a  "Chapman"  valve  with 
wedge-shaped  sides.  A  collar  holds 
the  valve  spindle  at  a  fixed  point;  and 
to  open  or  close,  the  valve  is  drawn  up 
or  lowered  by  turning  the  spindle.  When 
the  gate  reaches  the  bottom  of  the  pipe, 
a  wedge  on  the  lower  end  of  the  spindle 
causes  the  sides  to  move  laterally,  with 
sufficient  force  to  bring  a  strong  pres- 
sure against  the  valve-seat.  For  heavy 
work,  these  valves  are  made  with  a  rising  spindle  instead  of  a 
stationary  one.  This  possesses  the  distinct  advantage  of  indicating 
at  a  glance  whether  they  are  opened  or  closed,  while  one  cannot  tell 
by  looking  at  the  ordinary  gate  valve  whether  it  is  open  or  not. 

Check- Valves.  When  it  is  necessary  that  the  flow  should  always 
take  place  in  the  same  direction,  as  in  the  feed-pipe  of  a  boiler,  check- 
valves  are  used.  There  are  several  forms  shown  in  Fig.  40,  one  of 
which  has  a  similar  pattern  to  a  globe  valve,  with  a  ball  or  flat  valve, 
the  seat  being  parallel  to  the  direction  of  flow.  The  valve  is  held  in 
place  by  its  own  weight,  and  by  the  pressure  of  the  fluid  in  case  of  a 
reverse  flow.  In  the  swinging  check-valve,  the  seM  is  at  an  angle 


Fig.  39.    "Chapman"  Gate  Valve 
with  Wedge-Shaped  Sides. 


BOILER  ACCESSORIES 


39 


of  about  45  degrees  to  the  direction  of  flow.  It  is  fitted  somewhat 
loosely  where  it  is  fastened  to  the  swinging  arm,  so  that  it  may  prop- 
erly seat  itself.  This  form  is  usually  preferred,  as  it  offers  less 
resistance  to  flow  and  there  is  less  chance  for  impurities  to  lodge  on 
the  valve-seat.  When  a  check-valve  is  used  in  the  boiler-feed  pipe, 


ABC 
Fig.  40.    Types  of  Check-Valves.    ^i-Ball- Valve ;  .C-Flat  Valve;  tf-Swinging  Check- Valve. 

there  should  be  a  stop-valve  between  it  and  the  boiler,  which  can  be 
shut  in  case  the  check-valve  should  get  out  of  order. 

Materials.     For  pressures  under  200  Ibs.  per  square  inch,  cast 
iron  may  be  used  for  the  body  of  the  valve;  but,  for  economy,  it 
should  be  used  only  when  the  pressure  is  over  130  Ibs.     For  heavy 
work  it  is  frequently  necessary  to  have  a  massive  valve  that  cannot 
easily  be  broken.     In  such  a  case  a  cast-iron  body  is  the  most  suit- 
able thing.     The  valve-seat,  valves,  spindles,  stuffing-box,  glands, 
and     nuts    are 
usually  made  of 
gun-metal  or 
brass.  For  very 
high  pressures, 
especially      o  n 
steam  mains, 
cast  steel  is 
generally  used, 
with  gun-metal 
fittings  similar  to  those  enumerated  for  the  cast-iron  valves. 

Safety- Valves.  Safety-valves  are  used  for  reducing  the  pressure 
in  the  boiler  when  it  exceeds  a  certain  limit,  and  to  give  warning  of 
high  pressure.  There  are  several  different  types,  but  the  essential 
features  are  a  valve  opening  upward,  held  on  its  seat  by  a  weight  or 


Fig.  41.  Common  Type  of  Lever  Safety- Valve. 


40 


BOILER  ACCESSORIES 


spring.     When  the  pressure  in  the  boiler  exerts  a  force  greater  than 
that  holding  down  the  valve,  the  valve  will  open  automatically. 

The  lever  safety-valve  shown  in  Fig.  41  is  the  most  common  type 
for  stationary  work,  especially  for  small  boilers.  The  valve  is  held 
in  place  by  a  weight  at  the  end  of  a  lever.  The  force  required  to  lift 
the  valve  is  governed  by  the  location  of  the  weight  on  the  lever-arm. 

The  body  of 
the  valve  is 
usually  made 
of  cast  iron, 
the  seat  being 
of  brass.  An 


Fig.  42.    Diagram  for  Safety-Valve  Calculations. 


opening  on 
the  side  of  the 

valve  may  be  connected  with  the  feed-water  heater  or  drain,  if  the 
escape  of  steam  into  the  air  is  undesirable.  If  -the  valve  becomes 
leaky,  it  should  be  reground;  but  no  attempt  should  be  made  to 
make  it  tight  by  increasing  or  moving  the  weight  on  the  lever. 

The  amount  of  necessary  weight  on  the  lever,  and-  its  distance 
from  the  fulcrum,  can  be  determined  in  the  usual  manner  of  com- 
puting leverage  forces  and  moments,  remembering  that  weight 
times  weight-arm  is  equal  to  power  times  power-arm.  In  such  a 
valve  as  this,  power  is  the  steam  pressure,  and  the  power-arm  is  the 
distance  of  the  center  of  the  valve  from  the  fulcrum.  There  are  four 
weights  acting  downward — -the  ball,  the  lever-arm,  the  valve,  and  the 
spindle — and  in  the  process  of  computation  the  weight  and  leverage 
of  each  must  be  taken  into  account. 

Suppose,  for  example,  that  we  have  a  lever  safety-valve  such  as 
is  illustrated  in  outline  in  Fig.  42,  and  that  we  know  the  following  con- 
ditions: the  ball  weighs  125  Ibs.,  and  is  suspended  at  the  end  of  the 
lever  48  inches  from  the  fulcrum ;  the  valve  and  valve  spindle  together 
weigh  18  Ibs.,  and  are  4J  inches  'from  the  fulcrum;  the  lever-arrn 
itself  weighs  50  Ibs.  If  the  valve-seat  is  5  inches  in  diameter,  at  what 
pressure  will  the  valve  blow  off,  ignoring  the  friction  of  the  stuffing- 
box  and  fulcrum  pivot? 

The  center  of  gravity  of  the  lever-arm  must  be  determined  from 
the  drawing  (Fig.  42),  and  this  is  found  to  be  20  inches  from  the 


BOILER  ACCESSORIES 


41 


fulcrum      The  leverage  of  the  weights  acting  downwards  is  then 
follows  : 


as 


Ball 125  X  48    -  6,000 

Lever 50  X  20    =  1,000 

Valve  and  Stem 18  X    4£  = 81 

Total  moment =  7,081  inch-pounds. 


Now,  if  the  valve-seat  diameter  is  5  inches,  the  area  of  the  valve 


will  be 


TT  D2       3.1416X25 


=  19.63  sq.  in.     The  total  moment  to 


4  4 

be  overcome  is  7,081  inch-pounds,  and  its  distance  from  the  fulcrum 
is  4J  inches.     Therefore  the  necessary 
upward  pressure  on  the  valve   will  be 
_7,OS1  = 

4* 

the  valve  is  19.63  sq.  in.,  then  the 
necessary  pressure  in  pounds  per 
,573.5 


Ibs.      If  the  area  of 


square  inch  would  be 


80  Ibs., 


19.63 

approximately.  That  is,  this  safety- 
valve  would  blow  off  when  the  boiler 
pressure  reached  80  Ibs.  per  square  inch. 
If  it  is  desired  to  design  a  valve 
that  will  blow  off  at  known  pressure, 
the  same  principles  will  apply,  but  the 
computations  will  be  figured  in  the  re- 
verse order.  The  area  of  the  valve, 
times  the  boiler  pressure,  would  give 
the  total  lifting  force ;  and  this,  multi- 
plied by  its  leverage,  would  give  the 
lifting  moment,  which  would  be  re- 
sisted by  the  downward  moment  of  the 
combined  weights  of  valve,  valve-stem, 
lever,  and  ball.  If  the  moments  of  the  lever,  valve,  and  valve-stem 
were  known,  the  rest,  of  course,  would  be  made  up  by  the  ball. 
If  the  length  of  the  lever-arm  were  known,  then  the  weight  of  the  ball 
would  be  varied  to  correspond;  and,  conversely,  if  the  weight  of  the 
ball  were  fixed,  the  length  of  the  lever  must  be  made  to  correspond. 


Fig.  43.    "Crosby" 

for  Stationary 


-Valve 


42 


BOILER  ACCESSORIES 


The  lever  safety-valve  has  several  defects.  It  does  not  close 
promptly  when  the  pressure  is  reduced;  and  it  is  likely  to  leak  after 
it  is  closed,  and  may  readily  be  overloaded,  or  even  wedged  on  its 
seat.  It  is  essential  that  a  safety-valve  should  be  automatic,  certain 
in  its  action,  and  prompt  in  opening  and  closing  at  the  required 
pressure.  It  must  be  one  that  can  be  relied  upon  under  all  circum- 
stances. 

The  pop  safety-valve  fulfils  the  above  requirements  better  than 
those  of  the  lever  type.  Pop  valves  open  when  the  steam  pressure 

is  sufficient  to  overcome 
the  tension  of  the  spring. 
Fig.  43  shows  a  "Crosby" 
pop  safety-valve  for  sta- 
tionary service.  The 
valve  C  is  connected  by 
the  flange  B  to  the  cen- 
tral spindle  A,  and  is  held 
down  on  its  seat  by  the 
pressure  of  the  spring  S. 
The  valve  C  is  provided 
with  wing  guides  and  an 
annular  lip  E.  The 
guides  fit  smoothly  into 
the  seating  D,  upon 
which  the  valve  rests. 
The  seats  of  the  valve 
have  an  angle  of  45  de- 
grees. The  under  face  of  the  lip  E,  together  with  the  seating, 
forms  a  small  chamber  through  which  all  the  steam  must  pass 
to  the  open  air.  A  number  of  small  holes  drilled  vertically  through 
the  flange  F,  connect  with  the  chamber  and  allow  part  of  the 
steam  to  escape.  The  action  of  the  valve  is  regulated  by  the  screw 
ring  G,  which  allows  more  or  less  steam  to  escape  through  the  holes  in 
the  flange  F,  Raising  the  screw  diminishes,  and  lowering  it  increases, 
the  area  of  the  holes.  If  the  loss  of  steam  is  too  great  when  the 
valve  blows,  turn  the  screw  ring  down. 

Safety-valves  should  be  connected  directly  to  the  boiler  without  any 
pipe  or  elbow.  They  should  be  tried  every  day  by  means  of  the  lever. 


Fig.  44.    "Ashton"  Valve  with  Pop  Regulator  for 
Stationary  Boilers. 


BOILER  ACCESSORIES 


•43 


The  valve  shown  in  Fig.  44  for  stationary  boilers,  is  made  by  the 
Ashton  Valve  Company.  The  general  principles  are  those  of  all  pop 
safety-valves.  The  valve-seat  is  made  of  composition  or  nickel,  and 
with  a  bevel  of  45  degrees,  as  is  the  United  States  Government  stand- 
ard. The  pop  chamber  is  surrounded  by  a  knife-edge  lip,  which 
wears  down  in  proportion  with  the  seat,  thus  keeping  the  outlet  of  the 
same  relative  proportions,  giving  a  constant  amount  of  pop. 

The  amount  of  pop — that  is,  the  difference  of  pressure  between 
the  opening  and  the  closing  of  the  valve — is  regulated  from  the  out- 


Fig.  45. 


'Star  Marine"  Pop  Safety- Valve, 
with  Cam  Lever. 


Pig.  46.  "Ashton"  Safety- Valve  for 
Locomotive  Boilers,  with  Pop  Regula- 
tors on  Each  Side,  and  Top  Muffler. 


side  by  means  of  the  screw-plug  pop  regulator  shown  at  H  in  Fig.  44. 
If  more  pop  is  desired,  turn  the  regulator  so  that  S  will  be  more  nearly 
perpendicular.  To  lessen  pop,  make  0  more  nearly  perpendicular. 
The  springs  are  made  of  Jessop's  best  steel. 

The  inlet  and  outlet  are  both  on  the  same  casting,  so  that  the 
valve  may  be  taken  apart  to  be  cleaned  or  repaired,  without  disturbing 
the  boiler  connection.  It  has  a  lock-up  attachment,  so  that  the  regu- 
lating parts  cannot  be  tampered  with,  either  by  accident  or  by  design, 
The  spring  is  encasea,  thus  protecting  it  from  the  steam. 


44 


BOILER  ACCESSORIES 


The  "Star  Marine"  pop  safety-valve  is  shown  in  Fig.  45.  It 
has  a  bevel  seat,  and  is  provided  with  a  cam  lever  by  which  it  may  be 
raised  from  its  seat  when  there  is  no  steam  pressure.  The  outlet  of 
the  valve,  if  desired,  may  be  piped  to  the  supply  tank  or  to  any  other 
point. 

Safety-valves  for  locomotive  boilers  must  be  made  of  heavy  material 
to  stand  the  severe  usage.  They  should  be  so  constructed  that  they 
will  not  cock  or  tilt.  The  "Ashton"  valve  shown  in  Fig.  46  is  con- 


rig.  47.    "Holt"  Reducing  Valve  with  Diaphragm  Regulating  Pressure. 

structed  so  that  the  amount  of  pop  can  be  regulated  by  merely  turning 
the  two  posts  marked  2  and  3  to  the  right  or  left.  The  noise  of  the 
steam  escaping  from  the  ordinary  safety-valve  is  disagreeable,  and  in 
some  States  the  law  requires  the  use  of  the  muffler  safety-valve.  The 
Ashton  valve  shown  in  Fig.  46  has  a  top  muffler. 

Reducing  Valves.  Sometimes  steam  is  desired  at  a  lower  pres- 
sure than  that  of  the  boiler.  For  instance,  a  small  low-pressure  engine 
may  be  run  by  steam  taken  from  the  same  boiler  that  supplies  a 
higher-pressure  engine.  This  reduction  is  accomplished  by  throttling 
the  steam  by  means  of  reducing  valves.  These  are  arranged  to  be 


THE 
'NIVERSITY 

OF 

«UFORNl£- 


BOILER  ACCESSORIES  45 

operated  automatically  so  that  the  pressure  can  be  reduced  and  a 
constant  pressure  in  the  steam  pipes  maintained.  There  are  several 
forms  in  general  use. 

In  the  "Holt"  valve,  Fig.  47,  the  low-pressure  steam  acts  on  the 
lower  side  of  the  diaphragm;  and  the  weight,  which  may  be  set  so  as 
to  cause  the  desired  pressure,  acts  on  the  other.  The  movement  of 
this  diaphragm  causes  a  balanced  valve  to  move  to  or  from  its  seat. 
The  valve  opens  until  the  steam  pressure  equals  the  weight  above. 
The  pressure  in  the  main  steam  pipe  does  not  affect  the  movement 
of  the  valve.  It  depends  only  upon  the  pressure  on  the  two  sides  of 
the  diaphragm. 

Another  form,  the  "Mason,"  is  shown  in  Fig.  48.  A  spring,  which 
may  have  its  tension  altered  by  a  key,  takes  the  place  of  the  lever  and 
weight  in  the  Holt  valve.  When  the  pressure  in  the  low-pressure 
system  has  risen  to  the  required  point,  which  is  determined  by  the 
spring,  the  valve  closes,  and  no  more  steam  is  admitted  until  the 
pressure  falls  sufficiently  to  open  the  valve  again. 

In  another  form,  a  piston  acted  on  by  the  low-pressure  steam 
regulates  the  opening  of  a  balanced  valve,  and  this  maintains  a  con- 
stant steam  pressure. 

In  the  "Foster"  reducing  valve,  the  valve  is  held  open  by  the 
spring  and  levers,  until  the  steam  pressure  at  exit  presses  on  the  dia- 
phragm sufficiently  to  close  the  valve.  The  valve  is  held  open  so  as 
to  admit  just  the  proper  amount  of  steam  to  maintain  the  required 
pressure. 

When  a  reducing  valve  is  used,  a  stop-valve  should  be  put  in  to 
prevent  flow  when  steam  is  not  in  use. 

BLOW=OUT  APPARATUS 

Boiler  feed-water,  if  taken  from  rivers  or  ponds,  is  likely  to 
contain  vegetable  matter  as  well  as  solid  materials.  The  vegetable 
matter  will  usually  float  to  the  surface,  while  the  solids  will  collect  at 
the  bottom.  To  keep  the  boiler  clear  of  such  sediment,  it  is  neces- 
sary to  provide  two  blow-outs — a  surface  blow-out,  to  take  care  of 
what  rises  to  the  top;  and  a  bottom  blow-out,  to  take  out  the  sediment 
that  collects  at  the  bottom  of  the  boiler.  The  surface  blow-out 
usually  consists  of  a  dish  or  funnel-shaped  receptacle  set  with  its  face 


46 


BOILER  ACCESSORIES 


vertical,  as  shown  in  Fig.  49.  When  the  water-level  is  in  line  with 
this  blow-out  opening,  the  opening  of  the  valve  at  the  bottom  will 
skim  the  impurities  from  the  surface  of  the  water  quite  readily.  Oil 

may  get  into  the  boiler  through  the  feed- 
water,  and  a  considerable  portion  of  it 
can  be  removed  in  this  manner. 

The  bottom  blow-out  consists  merely 
of  a  pipe  leading  from  the  bottom  of  the 
boiler  outward.  Both  these  blow-outs 
may  be  connected  into  one  outlet. 

In  water-tube  boilers  a  mud-drum 
is  usually  installed,  which  readily  collects 
the  solid  matter,  and  the  bottom  blow- 
out is  then  connected  with  this  mud-drum. 
Fig.  50  shows  an  arrangement  of  surface 
and  bottom  blow-outs  as  usually  installed 
on  a  Scotch  boiler  of  the  marine  type. 

If  the   feed-water  contains  salt,  which 
may  frequently  happen   in  marine  prac- 
tice, it  is  necessary  that  the  boiler  should 
Fig.  48.  "Mason"  Reducing  vaive.  frequently  be  blown  out   in  order  to  re- 

Pressure  Regulated  by  Means 

of  a  spring.  move  the  excess  of  salt.  The  density  of  the 

boiler  water,  if  salt  feed  is  used,  should  be  carefully  determined  by  a 
salimeter.  The  loss  due  to  this  frequent  blowing  out  is  considerable, 
as  a  large  amount  of 
heat  is  necessarily  wasted ; 
but  it  cannot  be  avoided, 
except  by  the  use  of 
fresh  water,  which  some- 
times may  be  impossible 
at  sea. 

The  blow-out  pipe 
leading  from  the  bottom 
of  an  externally-fired 

boiler  through   the   brick          Fig  49     surface  Blow-Out  Installed  in  Boiler. 

setting,   if    not  properly 

protected,  may  be  burned  off,  owing  to  the  heat  of  the  fire.    This 

pipe  is  frequently  covered  with  asbestos  or  other  fire-resisting  material ; 


BOILER  ACCESSORIES 


47 


48 


BOILER  ACCESSORIES 


but  it  can  be  best  protected  by  the  means  shown  in  Fig.  51.  A  pipe 
connected  to  the  boiler  slightly  below  the  water-level,  runs  out  through 
the  brick  setting  and  connects  into  the  main  blow-out  pipe.  This 
causes  a  circulation  of  water  continually  to  pass  through  the  system, 
and  prevents  destruction  of  the  blow-out  pipe.  When  it  is  necessary 
to  use  the  bottom  blow-out,  the  valve  A  is  closed,  and  the  blow-off 
valve  B  is  opened;  otherwise,  B  is  closed,  and  A  is  open  while  the 
water  circulates. 

The  blow-out  pipe  is  usually  shut  off  by  a  cock,  which,  although 
not  so  easily  operated  as  a  valve,  is  more  trustworthy.  Frequently 
both  a  cock  and  a  valve  are  provided.  Should  a  small  particle  of 

sediment  lodge  on 


the    valve-seat,    it 
\   ^Water  Level  woukl   be   impossi_ 

ble  to  close  the 
valve  tightly,  and 
a  considerable  leak- 
age would  result, 
while  an  inspection 
of  the  valve  would 
not  indicate 
whether  it  were 
completely  closed 
or  not.  But  a 
glance  reveals  the  fact  whether  or  not  a  cock  is  tightly  closed.  The 
cock  is  likely  to  stick  because  of  corrosion  or  unequal  expansion, 
but,  if  frequently  opened,  this  difficulty  is  not  of  great  weight. 
The  plug  and  casing  of  the  cock  should  not  be  made  of  the  same 
material,  as  in  that  case  they  will  more  readily  stick  if  the  cock 
remains  closed  any  length  of  time. 


Boner 


Fig.  51.     Method  of  Protecting  Bottom  Blow-Out  Pipe  by 
Means  of  Circulation  Pipe  Connected  to  Boiler. 


FEED  APPARATUS 

Perhaps  the  most  important  of  all  auxiliaries  connected  with  the 
boiler  is  the  feed  apparatus.  This  is  vital;  for,  if  the  feed  is  inter- 
rupted and  the  water  runs  low  in  the  boiler,  not  only  is  there  danger 
of  damaging  the  boiler  itself,  but  a  disaster  may  follow  of  far  greater 
concern.  For  marine  purposes — and  the  same  is  true  to  a  consider- 


BOILER  ACCESSORIES  49 


able  extent  in  stationary  work — at  least  two  independent  feed  systems 
should  be  provided.  In  marine  work,,  the  main  feed-pump  draws 
water  from  the  filter  box  or  feed-water  heater,  and  pumps  it  into  the 
boilers  under  ordinary  conditions.  There  should  be  a  by-pass  around 
this  pump,  and  the  feed  line  should  be  connected  by  means  of  a  valve 
to  what  is  known  as  the  donkey  pump,  which  may  be  used  for  auxiliary 
feed  purposes  in  case  the  main  pump  is  damaged  or  needs  repairs  in 
any  way. 

Both  these  pumps  draw  from  and  discharge  into  the  same  feed 
line;  but,  to  provide  against  emergencies,  there  is  usually  a  cross- 
connection  to  the  sea,  so  that  sea  water  may  be  had  if  necessary. 
While  in  port,  when  the  main  engines  are  not  running,  and  conse- 
quently when  the  feed-water  cannot  be  heated  economically,  an  in- 
jector is  almost  invariably  used.  On  land  it  is  usually  considered 
sufficient  to  install  an  injector  in  addition  to  the  feed  pump,  although 
in  large  plants  an  auxiliary  feed  pump  should  be  installed  as  well.  In 
a  small  plant  the  fireman  usually  attends  to  the  water;  but  on  board 
ship  and  in  large  plants,  a  water  tender  is  usually  provided,  whose 
business  it  is  to  keep  the  water  in  the  boiler  at  the  proper  level.  His 
task  may  be  materially  lessened  by  some  automatic  arrangement,  so 
that  if  the  water  discharged  into  the  hot  well  from  the  condenser  rises 
above  the  normal  level,  a  float  will  open  the  valve  leading  to  the  feed- 
pump and  increase  the  rapidity  of  its  stroke.  This  will  reduce  the 
level  of  the  hot  well  or  filter  box,  as  the  case  may  be. 

Such  an  arrangement  as  this  will  keep  a  fairly  uniform  level  of 
water  in  the  boilers;  and  if  a  surface  condenser  is  employed,  and  all 
the  condensation  is  pumped  back  into  the  boilers,  the  water-level  will 
remain  constant  except  for  slight  leakages  of  steam  and  for  the  possi- 
bility of  improper  action  of  the  feed-pump.  Leakage  of  steam  can 
be  made  up  from  the  supply  of  fresh  water.  At  sea,  salt  water  may  have 
to  be  used  for  this  purpose  although  its  use  is  objectionable. 

There  is  a  considerable  difference  of  opinion  as  to  where  the  feed- 
water  should  be  introduced  into  the  boiler,  although  the  consensus 
of  opinion  seems  to  be  that  it  should  enter  not  far  from  the  water-line. 
In  stationary  practice,  the  feed-water  is  introduced  at  the  rear  of  the 
boiler  near  the  bottom;  but  this  is  open  to  grave  objections,  for  the 
feed-water,  being  comparatively  cool  and  being  introduced  into  the 
coldest  part  of  the  boiler,  naturally  tends  to  become  dead  water  and  to 


50  BOILER  ACCESSORIES 

retard  proper  circulation  which  is  essential  to  economical  steaming 
and  often  essential  to  the  safety  of  the  boiler  itself. 

The  best  place  for  introducing  the  feed-water  will  naturally 
depend  upon  the  type  of  boiler,  and  the  service  for  which  it  is  intended. 
If  the  entering  water  is  of  high  temperature,  it  might  enter  near  the 
bottom  of  the  boiler.  But  if  the  feed -water  is  comparatively  cold  - 
and  it  is  always  colder  than  the  water  in  the  boiler  and  the  surround- 
ing steam  if  the  circulation  is  good — great  care  must  be  taken  that 
it  does  not  strike  directly  against  the  hot  boiler-plates,  as  it  might 
thereby  cause  local  contraction  and  possibly  a  serious  leak,  and  it 
should  be  introduced  in  such  a  way  as  to  make  sure  of  its  aiding  the 
natural  circulation  of  the  boiler. 

The  higher  the  steam  pressure  in  the  boiler,  the  more  difficult 
becomes  the  problem  of  feed,  and  the  more  danger  there  is  of  injury 
to  the  boiler  by  the  comparatively  cold  feed-water  striking  hot  plates. 
It  is  a  universal  practice  in  marine  work,  and  a  common  practice  on 
land,  especially  for  internally-fired  boilers,  to  cause  the  feed  to  enter 
above  the  water-level  near  the  center  of  the  boiler;  then  branching 
off  into  two  pipes,  one  leading  to  each  side  through  the  steam  space 
until  the  side  of  the  boiler  is  reached;  and  then  running  downward 
toward  the  bottom.  The  feed -water,  which  very  likely  has  been 
previously  heated  by  a  feed-water  heater,  is  still  further  heated  by  its 
passage  through  this  feed-pipe,  which  is  in  direct  contact  with  the  live 
steam  of  the  boiler.  This  internal  feed-pipe,  turning  down  at  the  sides, 
causes  the  water  to  strike  the  outer  shell  of  the  boiler  which  is  the 
most  remote  from  the  fire,  and  this  downward  motion  materially 
assists  the  circulation  in  the  boiler.  When  this  arrangement  of  feed 
is  adopted  (see  Fig.  50),  care  must  be  taken  that  the  lower  end  of 
the  feed-pipe  is  well  below  the  low-water  level.  If  the  end  of  the 
pipe  is  alternately  immersed  in  water  and  then  exposed  to  steam, 
violent  explosions  in  the  pipe  are  likely  to  follow,  although  they  are 
likely  to  do  nothing  more  serious  than  break  an  elbow  or  frighten 
the  attendants. 

In  stationary  practice,  it  is  quite  common  to  admit  the  feed-water 
into  the  steam  space  through  a  horizontal  pipe  entering  it  through  the 
tube-plate  a  few  inches  below  the  low-water  level,  and  terminating  in 
a  perforated  pipe  of  large  diameter.  This  method  distributes  the  feed- 
water  admirably,  and  allows  it  to  become  considerably  heated  before 


BOILER  ACCESSORIES 


51 


it  reaches  the  bottom  of  the  boiler.  If  the  feed-water  contains  a  con- 
siderable amount  of  magnesia  or  calcium  carbonate,  holes  so  arranged 
in  the  feed-pipe  are  likely  to  become  clogged  and  the  feed  interrupted. 
Water  of  this  sort  should  be  fed  into  a  trough,  or  the  feed-pipe  be 
opened  at  the  top  by  a  long  slot,  so  that  the  feed-water  may  over- 
flow. The  trough  in  this  case  forms  an  admirable  mud-drum  or 
sediment  collector. 

In  internally-fired  boilers  of  the  "Cornish"  or  "Lancashire"  type, 


Fig.  52.    Steam-Driven  Boiler  Feed-Pump. 

• 

the  feed  is  usually  delivered  near  the  bottom  through  a  horizontal 
pipe — either  through  the  front  end  or  by  a  vertical  pipe  through  the 
crown.  This  method  is  not  conducive  to  the  best  circulation. 

In  addition  to  these  effects  on  circulation,  there  are  other  grave 
objections  to  introducing  feed -water  near  the  bottom  of  the  boiler;  for, 
should  anything  happen  to  the  feed-pump,  or  a  piece  of  scale  lodge 
under  the  check-valve,  the  water  might  be  almost  entirely  blown  out 
of  the  boiler  before  the  difficulty  could  be  discovered  or  remedied. 


52 


BOILER  ACCESSORIES 


If  the  pipe  enters  in  the  vicinity  of  the  low-water  level,  no  water  could 
be  drawn  out  below  this  point. 

The  feed  supply  should  always  be  regulated  so  as  to  keep  the 
water-level  as  nearly  stationary  as  possible;  this  is  not  only  much 
more  economical,  but  also  far  better  for  the  boiler,  than  to  wait  for  the 
water-level  to  fall  and  then  feed  a  few  inches  rapidly.  The  sudden 
introduction  of  a  large  volume  of  comparatively  cold  feed -water,  causes 
local  contraction  of  the  plates,  and  hence  tends  to  cause  leakage: 


Fig.  53.    Section  of  "Worthington"  Duplex  Steam  Pump. 

moreover,  it  necessitates  irregular  firing  if  anything  like  a  uniform 
steam  pressure  is  to  be  maintained. 

Sometimes  the  feed-water  is  forced  into  the  steam  space  in  the 
form  of  a  fine  spray.  In  this  way  it  not  only  is  thoroughly  heated 
before  mingling  with  the  water  in  the  boiler,  but  the  air  is  got  rid  of; 
and  salts,  such  as  sulphate  of  lime,  insoluble  at  high  temperatures, 
are  immediately  precipitated.  But  the  advantage  of  introducing  the 
feed-water  in  a  body  so  as  to  produce  useful  circulating  currents, 
should  not  be  overlooked. 


BOILER  ACCESSORIES    '  53 

If  several  boilers  are  attached  together  in  the  form  of  a  battery, 
each  should  be  supplied  with  an  independent  connection  to  feed- 
pipe. Otherwise  a  damage  to  the  feed-pipe  in  one  boiler  might  affect 
the  others.  Moreover,  if  several  boilers  are  fed  from  one  pipe,  the 
pressure  in  each  of  them  being  slightly  different,  an  excess  of  water 
will  naturally  be  fed  into  the  boiler  having  the  least  pressure,  whereas 
it  is  usually  the  case  that  the  most  water  is  needed  in  the  boiler  hav- 
ing the  greatest  pressure.  The  automatic  float  previously  referred  to, 
can  regulate  the  amount  of  water  fed  into  boilers  only  in  a  general 
way,  through  providing  a  method  by  means  of  which  all  the  con- 
densation is  fed  back  into  some  of  the  boilers;  but  the  quantity  of 
feed  which  is  led  into  each  individual  boiler  must  be  watched  and 
regulated  by  the  water  tender,  who  can  open  or  close  the  individual 
valves  as  desired. 

Pumps.  Boilers  are  usually  fed  by  a  small,  direct-acting 
steam  pump  placed  near  the  boiler.  Although  these  pumps  require 
a  large  steam  supply  per  horse-power  per  hour,  the  total  amount  of 
steam  used  is  small  because  the  work  done  is  small  A  more  eco- 
nomical pump  is  the  power  pump  driven  by  the  large  steam  engine; 
but  in  this  case  the  rate  at  which  water  is  supplied  is  not  easily  regu- 
lated to  the  demand  of  the  boiler.  Power  pumps  are  usually 
arranged  to  pump  a  larger  quantity  of  water  into  the  boiler  than  is 
required,  the  excess  of  water  being  allowed  to  flow  back  into  the 
suction  pipe  through  a  relief  valve.. 

The  pump  shown  in  Fig.  52  is  well  adapted  for  feeding  boilers. 
In  Fig.  53  is  shown  the  section  of  a  duplex  "Worthington"  steam  pump. 
The  action  of  each  of  these  two  types  is  similar.  Steam,  controlled 
by  valves,  drives  the  piston  in  the  steam  cylinder,  which  moves  the 
plunger  in  the  water  cylinder,  since  both  are  fastened  to  the  same  rod. 
The  movement  of  the  plunger  forces  a  part  of  the  water  in  front 
of  it  up  through  the  valves  into  the  air-chamber,  and  through  the 
pipes  into  the  boiler.  On  account  of  the  partial  vacuum  caused  by  the 
movement  of  the  plunger,  water  will  be  drawn  from  the  suction  pipe, 
through  the  valves,  into  the  pump  cylinder,  filling  the  space  left  by 
the  movement  of  the  plunger.  During  the  return  stroke,  this  water 
is  forced  up  into  the  air-chamber,  and  a  like  quantity  enters  the  other 
end  of  the  pump  cylinder.  The  valves  are  kept  on  the  seats  by  light 


54 


BOILER  ACCESSORIES 


STEAM 


springs,  until  the  pressure  on  the  bottom  side  is  sufficient  to  lift  them 
and  allow  water  to  flow  through. 

When  two  pumps  are  placed  side  by  side,  and  have  a  common 
delivery  pipe,  the  machine  is  called  a  duplex  pump.     It  is  usual  to  set 

the  steam  valves  so  that 
when  one  piston  is  at  the 
end,  the  other  is  at  the  mid- 
dle of  its  stroke.  A  duplex 
pump  having  a  large  air- 
chamber  and  valves  set  to 
act  in  this  manner,  delivers 
water  with  an  approxi- 
mately constant  velocity. 

Injectors.  Water  may  be 
forced  into  a  boiler  by  an 
injector  or  inspirator.  By 
means  of  this  instrument, 
the  energy  of  a  jet  of  steam 
is  used  to  force  the  water 
into  the  boiler.  That  there 
is  sufficient  energy  to  do 
this  work  is  evident  from 
the  fact  that  each  pound  of 
steam,  in  condensing,  gives 
up  about  1,000  B.  T.  U., 
and  a  B.  T.  U.  is  equiva- 
lent to  778  foot-pounds. 
Not  all  the  energy  of  the  jet 
of  steam  is  used  in  forcing 
water  into  the  boiler;  some 
is  wasted,  and  much  is  used 
to  heat  the  feed-water. 

The  action  of  the  injector 
is  briefly  as  follows:  The  steam  escapes  from  the  boiler  with 
great  velocity,  and,  as  it  passes  through  the  cone-shaped  passage, 
draws  air  along  with  it,  thus  creating  a  partial  vacuum  in 
the  suction  pipe.  Atmospheric  pressure  forces  water  up  into  the 
suction  pipe,  and  the  jet  of  steam  which  it  meets  is  partly  condensed. 


OVERFLOW 

Fig.  54.    Sectional  View  of  "Hancock"  Injector. 


BOILER  ACCESSORIES 


55 


The  energy  of  the  jet  carries  the  water  along  with  it  into  the  boiler. 

Experiments  show  that  the  injector,  if  considered  as  a  pump, 
has  a  very  low  efficiency.  When  used  for  feeding  a  boiler,  it  has  a 
thermal  efficiency  of  nearly  100  per  cent,  since  all  the  heat  of  the  steam 
passes  to  the  water  except  STEAM 
the  slight  amount  lost  in 
radiation.  The  pump, 
however,  has  one  great  ad- 
vantage over  the  injector; 
it  can  force  hot  water 
from  a  heater  into  the 
boiler,  while  an  injector 
can  be  used  only  with  cold 
or  moderately  warm  water. 

Figs.  54  and  55  show 
the  interior  section  and 
exterior  of  a  "Hancock" 
inspirator.  To  inject  water 
to  the  boiler,  first  open 
overflow  valves  1  and  3; 
close  valve  2;  and  open 
starting  valve  in  the  steam 
pipe.  When  the  water  ap- 
pears at  the  overflow, 
open  2  one  quarter-turn, 
close  1,  and  then  close  3. 
The  inspirator  will  then  be 
in  operation.  When  the 
inspirator  is  not  working, 
open  both  1  and  3  to  allow 
water  to  drain  from  it. 

Both  temperature  and 
quantity  of  delivery  water 
can  be  varied  by  increas- 
ing or  decreasing  the  water  supply.  When  the  water  in  the  suction 
pipe  is  hot,  either  cool  off  both  pipe  and  injector  with  cold  water, 
or  pump  out  the  hot  water  by  opening  and  closing  the  starting  valve 
suddenly. 


OVERFLOW 

Fig.  55.    Exterior  View  of  "Hancock"  Injector. 


56  BOILER  ACCESSORIES 

Circulating  Apparatus.  There  is  always  more  or  less  danger  in 
starting  a  fire  under  a  boiler.  If  the  circulation  is  poor,  the  result 
will  be  that  not  only  will  the  water  be  of  an  uneven  temperature,  hot 
near  the  .top  and  cold  at  the  bottom,  but  the  boiler  shell  is  likely  to 
be  subjected  to  severe  strain,  owing  to  the  difference  of  temperature 
arising  from  the  stagnation  of  the  cold  water  near  the  bottom.  The 
fire  must  be  started  slowly,  and  a  considerable  time  consumed  in 
getting  up  steam.  To  overcome  the  difficulty  of  poor  circulation, 
several  mechanical  devices  have  been  applied. 

The  first  device  tried  was  a  hydro-kineter — a  sort  of  injector — in 
which  jets  of  steam  driven  through  a  conical  nozzle  drew  in  the  sur- 
rounding water.  This  was  so  arranged  as  to  induce  the  cold  water 
to  flow  from  the  bottom  toward  the  top,  where  it  was  more  intensely 
heated.  This  arrangement  is  efficient,  but  slow  of  action.  In  large 
marine  boilers — in  which  the  fire  is  cautiously  started,  as  is  proper — 
the  temperature  at  the  surface  of  the  water,  four  hours  after  lighting 
up,  has  been  found  to  be  as  high  as  205°,  while  at  the  bottom  it  was. 
only  73°.  Several  observations  with  a  hydro-kineter  ill  action  have 
shown  the  temperatures  to  be  205°  and  144°  respectively.  It  was 
six  hours  more  before  the  temperature  was  equalized  throughout. 

In  naval  vessels,  where  it  is  frequently  necessary  to  raise  steam 
rapidly,  this  device  is  altogether  too  slow.  It  has,  moreover,  two 
other  drawbacks.  There  must  be  an  auxiliary  boiler  under  steam 
pressure,  and  it  will  cease  to  act  when  the  temperature  and  pressure 
of  steam  in  the  main  boiler  has  reached  that  in  the  auxiliary  boiler. 
The  steam  jet,  in  the  American  Navy,  has  been  replaced  by  a  jet  of 
feed -water  forced,  through  a  conical  nozzle.  This  arrangement 
answers  very  well  so  long  as  steam  is  being  drawn  from  the 
boiler;  but  when  the  boiler  is  at  rest  and  steam  is  being  raised,  it  is 
inoperative. 

The  best  service  can  be  had  by  means  of  small  centrifugal  pumps 
fixed  beside  the  boilers,  which  take  water  from  the  bottom  of  the 
boilers  and  discharge  it  a  little  below  the  water-level.  The  pumps 
may  be  turned  by  hand  while  raising  pressure,  and  may  be  worked 
by  steam  when  sufficient  pressure  has  been  attained.  A  small  engine 
of  perhaps  1 J  horse-power  is  sufficient  to  give  a  proper  circulation  to 
a  large  boiler.  With  such  a  circulating  device,  steam  can  be  raised 
with  safety,  in  a  comparatively  short  time. 


BOILER  ACCESSORIES 


57 


Evaporators.  No  engine  can  be  run  without  a  certain  loss  of 
water,  due  either  to  a  slight  continuous  leakage  or  to  blowing  off.  In 
stationary  practice,  this  loss  can  be  readily  made  up  by  the  appli- 
cation of  fresh  water;  but  at  sea  it  is  seldom  possible  to  carry  a  suffi- 
cient amount  of  fresh  water,  and  the  make-up  must  be  had  either 
from  sea  water,  or  from  fresh  water  provided  by  the  use  of  an  evapora- 
tor. The  evaporator  is  really  a  small  boiler,  the  water  in  which  is 


OUTLET 


Cold 
Water 


Fig.  56.    Feed-Water  Heater, 
Closed  Type. 


Fig.  57.    Feed-Water  Heater, 
Open  Type. 


heated  by  a  steam  coil  supplied  from  the  main  boiler.  The  evaporated 
water — called  the  evaporation — passes  into  the  condenser  and  then 
becomes  a  part  of  the  regular  feed  water. 

In  a  single  evaporator,  if  the  evaporation  passes  directly  to  the 
condenser,  its  heat  is  lost  to  useful  work.  To  provide  a  more  econom- 
ical arrangement,  multiple  evaporators  are  installed,  which  consist  of 
a  series,  the  evaporation  from  the  first  passing  into  a  coil  in  the  bottom 
of  the  second;  the  water  in  the  second  condenses  the  evaporation 
from  the  first,  while  at  the  same  time  the  evaporation  from  the  first 


58 


BOILER  ACCESSORIES 


helps  to  heat  the  water  of  the  second.     The  steam  and  water  pass 
through  the  series  of  heaters  in  opposite  directions. 

It  is  a  rule  in  the  French  Navy,  to  provide  380  Ibs.  of  fresh  water 

per  hour  for  each 

-Exhaust Outlet  1,000    indicated 

horse-power;    this 
provides  for  a  loss 


Regulating 
tValv< 


Oil  Separai 


Ex.  Inlet 
Skimmer 


Perforated 
Plates 


Cold  Water  of  about  2  Per  cent 
without     drawing 

on  the  reserve  sup- 
ply, which  is  4,500 
Ibs.  for  the  same 
amount  of  power. 
The  evaporator 
may  be  arranged 
to  communicate 
with  a  low-pres- 
sure  valve-chest, 
in  which  case  the 
evaporation  may 
be  made  to  do 
work  in  a  low- 
pressure  cylinder 
of  a  triple-expan- 
sion engine  before 
entering  the  con- 
denser, or  it  may 
be  connected  with 
the  feed-water 
heater  if  the  ex- 
haust steam  is  in- 
adequate. 

FeecUWater 
Heaters.  The  in- 
troduction of  feed- 
water  at  a  high 
temperature  increases  the  economy  and  tends  to  prolong  the  life  of 
the  boiler.  The  injurious  effects  from  unequal  expansion  are  dimin- 


Oll  Separator 


Fig.  58. 


"Cochrane"  Combined  Feed- Water  Heater  and 
Purifier,  Open-Heater  Type. 


u    to 

a 

c/3    £ 

11 


S5    ^ 

§  ? 

«  -a 

0) 


BOILER  ACCESSORIES  59 

ished;  and  when  the  feed  is  warmed  by  exhaust  steam  or  by  the  waste 
gases  in  the  uptake,  the  saving  of  fuel  is  considerable. 

If  this  gain  comes  from  waste  gases  or  exhaust  steam,  which 
would  otherwise  make  no  return  for  their  heat,  the  gain  is  clear;  but 
there  is  no  gain  in  thermal  economy  by  heating  feed-water  with  live 
steam  directly  from  the  boiler. 

There  are  several  ways  of  heating  the  feed-water.  In  condensing 
engines,  the  feed-pump  discharges  from  the  condenser  into  the  hot 
well,  and  the  water  is  drawn  from  the  hot  well  at  a  temperature  of 
100°  to  140°  F.  This,  however,  if  the  pressure  is  over  100  Ibs.,  is 
entirely  inadequate;  and  for  the  best  economy,  feed -water  at  this 
temperature  should  be  passed  through  some  form  of  feed-water 
heater.  In  the  non-condensing  engines,  it  is  absolutely  necessary 
that  in  some  way  the  feed-water  should  be  heated  by  the  exhaust 
steam  or  by  waste  gases  from  the  chimney,  the  apparatus  in  the  first 
case  being  called  a  feed-water  heater,  and  in  the  second  an  economizer. 

The  feed-water  heater  may  be  arranged  so  that  it  will  not  only 
heat  the  water,  but  will  at  the  same  time  purify  it,  precipitating  the 
calcium  and  magnesia  salts,  which  collect  on  suitably  prepared  plates, 
and  gathering,  at  the  bottom  of  the  heater,  dirt  and  other  sediment 
that  would  injure  the  boiler. 

There  are  two  types  of  feed-water  heater — the  open,  which  is 
frequently  used  in  land  work;  and  the  dosed,  which  may  be  used 
either  on  land  or  at  sea.  In  the  open  heater,  the  steam  raises  the 
temperature  of  the  water  by  mingling  with  it  in  direct  contact.  The 
closed  type  of  heater  resembles  in  its  action  a  surface  condenser;  the 
steam  used  for  heating  purposes  surrounds  tubes  which  contain  the 
feed-water,  or  the  water  circulates  about  tubes  through  which  the 
heating  steam  passes. 

Fig.  56  shows  a  feed-water  heater  of  the  closed  type,  the  exhaust 
steam  heating  the  feed -water  within  the  tubes.  The  heater  shown  in 
Fig.  57  is  of  the  open  type,  the  feed -water  becoming  heated  and  depos- 
iting sediment  while  flowing  from  one  tray  to  another. 

The  "Cochrane"  heater,  Fig.  58,  is  a  combined  heater  and  puri- 
fier of  the  open-heater  type,  the  water  entering  at  the  top  and  flowing 
in  a  thin  sheet  over  a  series  of  trays.  The  exhaust  steam  enters 
through  the  oil  separator,  and  rising  among  the  trays,  heats  the  water 
to  about  210°  F,  the  action  being  similar  to  that  of  a  jet  condenser. 


60  BOILER  ACCESSORIES 

The  gases  held  in  solution  in  the  feed -water  are  liberated  by  the  heat, 
and  escape  into  the  atmosphere ;  while  the  mineral  impurities  in  solu- 
tion, which  cause  scale,  are  precipitated  by  the  heat,  and  are  deposited 
on  the  trays  instead  of  on  the  plates  and  tubes  of  the  boiler.  The 
impurities,  mud,  clay,  etc.,  settle  to  the  bottom,  because  of  the  large 
surface  and  consequent  low  velocity  of  the  feed -water  through  the 
heater,  and  are  readily  removed.  Coke,  hay,  etc.,  are  used  for  filters, 
a  strainer  being  constructed  so  that  the  hay  or  coke  will  not  enter 
the  pump.  The  impurities,  having  less  specific  gravity  than  the 
water,  collect  at  the  surface,  and  are  removed  by  flushing. 


E 


O      S5 

•< 

S5     ^ 


S    o 


BOILER  ACCESSORIES 

PART  II 


STEAM  SEPARATORS 

Priming.  Steam  is  said  to  be  wet  or  to  be  superheated,  according 
as  it  has  an  excess  of  moisture  or  an  excess  of  heat.  Wet  steam  not 
only  is  uneconomical,  because  it  carries  a  considerable  amount  of  heat 
into  the  engine  in  the  form  of  water,  which  cannot  do  useful  work, 
but,  if  a  considerable  amount  of  water  gets  into  the  engine,  it  is  really 
dangerous,  for  it  may  so  completely  fill  the  clearances  that  the  piston 
will  strike  a  blow  against  the  cylinder-head  sufficient  to  break  it.  The 
svater  in  the  pipes,  moreover,  may  <^ause  a  serious  hammering,  which 
lot  only  is  exceedingly  annoying,  but  may  be  actually  dangerous,  for  a 
severe  water-hammer  may  break  the  joints  of  the  steam  pipes,  and  a 
considerable  quantity  of  escaping  steam  at  high  pressure  would  be 
exceedingly  dangerous  to  the  lives  of  the  engine-room  attendants. 
This  especially  would  be  true  on  board  ship,  where  the  engine-room  is 
small,  the  supply  of  air  meager,  and  the  means  of  escape  limited. 

A  considerable  amount  of  water  may  be  deposited  in  a  sag  in  the 
pipe  line,  and  would  undoubtedly  remain  there  for  a  considerable 
length  of  time  if  the  pressure  in  the  boiler  did  not  fluctuate;  but  a 
sudden  rise  of  boiler  pressure  would  likely  cause  this  water  to  pass 
bodily  through  the  pipe  toward  the  engine.  Moisture  is  carried 
directly  from  the  boiler  as  a  result  of  priming.  This  is  caused  by 
steam  bubbles  which,  instead  of  bursting,  become  connected  on  the 
surface  of  the  water,  forming  a  foam,  half-liquid,  half-gaseous,  which 
fills  the  steam  space  and  passes  out  of  the  steam  pipe.  Priming  may 
be  due  to  fluctuations  of  boiler  pressure  or  to  the  presence  of  dirt,  oil, 
or  other  foreign  matter.  The  smaller  the  free  surface  of  the  water 
in  the  boiler,  the  more  likely  the  water  is  to  prime.  Boilers  will  fre- 
quently prime  badly  under  forced  draft,  when  otherwise  there  would 
be  little  trouble. 

Priming  may  be  detected  from  the  unusual  behavior  of  the  water 
in  the  gauge-glass,  or  from  the  hammering  in  the  steam  pipes  or 


62 


BOILER  ACCESSORIES 


cylinder.  To  avoid  a  breakdown  under  such  conditions,  the  speed  of 
the  engine  should  be  reduced,  the  drain-cocks  of  the  cylinders  and 
pipes  opened,  and  the  fires  eased  down.  Sometimes,  by  suddenly 
shutting  the  main  stop-valve,  the  pressure  in  the  boiler  can  be  in- 
creased sufficiently  to  overcome  the  difficulty. 

Almost  any  boiler  is  likely  to  prime  to  some  extent;  and  to  obtain 
as  dry  steam  as  possible,  several  devices  are  employed.  On  the  top 

of  stationary  boilers  and  locomotives,  a 
steam  dome  is  frequently  built,  from 
which  the  steam  is  drawn,  the  idea  being 
that  less  moisture  will  be  found  here  than 
if  the  steam  be  drawn  directly  from  the 
main  portion  of  the  boiler.  In  marine 
work,  and  sometimes  in  stationary  plants, 
a  dry-pipe  is  used  (see  Fig.  50).  This  is 
merely  a  large  pipe  inside  the  boiler,  from 
which  the  steam  is  drawn.  The  pipe  is 
near  the  top  of  the  boiler,  and  the  upper 
side  of  it  is  perforated  with  holes  through 
which  the  steam  may  pass.  A  consider- 
able amount  of  moisture  is  in  this  way 
prevented  from  leaving  the  boiler. 

The  moisture  in  steam  can  be  reduced 
by  the  familiar  process  of  superheating; 
but  if  this,  for  any  reason,  is  impractica- 
ble or  undesirable,  a  steam  separator  may 
be  used  for  the  purpose  of  extracting  the 
moisture  that  comes  from  the  priming  of 
the  boiler  or  from  condensation  in  the 
steam  pipe. 

Separators.  There  are  several  forms  of  separator;  but  all  are 
designed  on  the  general  principle  that  if  the  direction  of  the  steam 
current  is  suddenly  changed,  or  if  it  is  diverted  upward  and  then  down- 
ward, the  water  will  be  separated  from  the  steam  and  will  fall  to  the 
bottom  of  a  suitable  receptacle.  The  depth  of  water  collected  in  the 
bottom  of  the  separator  is  readily  indicated  by  a  gauge-glass,  and  it 
may  be  drawn  off  as  desired.  To  prevent  the  possibility  of  flooding 
the  separator,  it  is  well  to  connect  it  with  an  automatic  trap  which 


Fig.  59..   "Stratton"  Separator. 


BOILER  ACCESSORIES 


63 


will  empty  it  without  close  attention  from  the  engineer.  It  is  needless, 
of  course,  to  say  that  the  trap  from  this  separator  should  be  con- 
nected to  the  hot  well,  and  the  drip  should  be  returned  to  the  boiler 
with  the  loss  of  as  little  heat  as  possible. 

In  the  "Stratton"  separator,  Fig.  59,  the  steam 
enters  at  one  side  of  a  cylinder,  flows  down- 
ward, and  then  upward  through  a  pipe  in  the 
middle.  Dry  steam  escapes  from  a  pipe  near 
on  the  opposite  side  from  which  it 
enters.  The  separated  water  is  drained  at  the 
bottom. 

The  "Cochrane"  steam  separator,  shown  in 
section  in  Fig.  60,  is  of  the  baffle-plate  type. 
The  branches  for  the  entrance  and  exit  of 


—  —  the  top, 


Fig.  60.    Sectional  Elevation 
and  Plan  of  "  Coehrane  " 
Steam  Separator. 


Fig.  61.    Separator  Designed  for  Connection 
to  Main  Steam  Pipe  near  Engine. 


the  steam  project  from  each  side  of  the  spherical  head.  Another 
branch  from  the  bottom  provides  for  connection  with  the  well  The 
baffle-plate,  which  is  cast  as  a  part  of  the  head,  is  ribbed,  or  corrugated, 
and  has  ports  at  each  side  for  the  passage  of  steam.  The  area  of  the 
ports  is  large,  to  prevent  loss  by  friction.  A  small  pipe  is  inserted 
in  the  plate  on  the  outlet  side  at  the  bottom  of  the  baffle-plate,  to  drain 


64 


BOILER  ACCESSORIES 


any  condensation  in  the  outlet  chamber.  Steam,  entering  at  the  left- 
hand  opening,  strikes  the  baffle-plate  and  passes  to  the  outlet  chamber 
by  means  of  the  two  side  passages,  as  shown  in  the  plan,  Fig.  60. 

A  form  of  separator  which  is  fitted  to  the  main  steam  pipe  near 
the  engine,  is  shown  in  Fig  61.  Steam  enters  at  A  and  strikes  the 
dash-plate  B-,  any  water  coming  with  the  steam  is  separated  and  falls 
to  the  bottom.  The  steam  takes  the  direction  indicated  by  the  arrows, 
and  flows  out  at  D.  This  separator  is  fitted  with  a  gauge-glass  which 
is  similar  to  a  boiler  gauge-glass. 

,  STEAM  TRAPS 

Steam  traps  are  used  for  collecting  the  water  of  condensation 
from  steam  pipes.  They  consist  of  a  receptacle  with  an  inlet  and 

outlet  valve  so  arranged 
that  the  condensation 
which  collects  may  flow 
out,  but  steam  cannot 
pass. 

In  the  float  trap  shown 
in  Fig.  62,  the  float  rises 
and  falls  with  the  change 


Fig.  62.    Simple  Steam  Trap  Operated  by  Float. 


in.  water-level.  When  the  water-level  rises  above  a  certain  point, 
the  float  opens  the  discharge  valve.  The  trap  shown  in  Fig.  63  is 
similar,  the  float  being 
replaced  by  a  weight 
W,  which  is  nearly 
counterbalanced  b  y 
the  weight  T.  The 
raising  of  PFby  the  wa- 
ter opens  the  valve  V. 
There  are  other 
forms  called  bucket 
traps.  In  the  one 
shown  in  Fig.  64,  the 
water  enters  at  W.  While  there  is  only  a  little  water  around 
the  bucket  F,  it  floats,  and  the  valve  V  is  closed ;  but  when  the 
water  rises  high  enough  to  flow  over  the  edge,  the  weight  of  water  in  the 
bucket  causes  it  to  sink,  and  opens  the  valve  V.  Water  is  forced  up 


Fig.  63.    Steam  Trap  Operated  by  Nearly  Counter- 
balanced Weight.  * 


BOILER  ACCESSORIES 


65 


Fig.  64.    Bucket  Type  of  Steam  Trap. 


the  passage  M,  and  out  through  the  pipe  N,  by  the  pressure  of  the 

steam  on   the   sur- 
face  of   the    water 

surrounding      the 

bucket. 

Another    form 

of  trap,  called   the 

differential  steam 

trap,  depends  upon 

a    head    of    water 

acting  on  a  flexible 

diaphragm.    Water 

enters  at  either  top 

or   bottom   by    the 

pipes    E,    Fig    65. 

When     the    water- 
level    rises,  it    fills 

the  chamber  G  and  the  pipe  N.    This  causes  a  pressure  on  the  under 

side  of  the  diaphragm  greater  than  that  caused  by  the  spring  II, 

which  spring  acts  on  the  upper 
side  of  the  diaphragm  and  tends 
to  keep  the  valve  open.  While 
the  pressure  below  the  diaphragm 
preponderates,  the  valve  P  re- 
mains closed.  When  the  water 
rises  and  fills  the  chamber  J  so 
as  to  flow  down  the  pipe  M ,  the 
water-pressure  on  the  upper  and 
lower  side  of  the  diaphragm  will 
become  equal,  because  the  head 
of  water  in  M  is  practically 
the  same  as  that  in  N.  The 
spring  will  now  open  the  valve  P, 
and  water  will  be  discharged 
from  the  pipe  7.  When  the 
head  in  M  falls,  the  pressure  on 

Fig.  65.  Differential  Steam  Trap.  Operated  by  .  L    . 

Water-Pressure  on  a  Flexible  Diaphragm.      the  under  Side  of  the  diaphragm 

again  becomes  greater,  and  the  valve  accordingly  closes. 


66 


BOILER  ACCESSORIES 


Return  Traps.  Traps  that  are  used  for  returning  water  of  con- 
densation to  the  boiler  are  called  return  traps.  There  are  a  variety 
of  forms,  but  the  principle  of  action  in  all  is  similar,  and  is  shown  in 
Fig.  66.  B  represents  the  boiler,  and  T  the  trap,  which  is  placed  a 
few  feet  above  the  boiler.  The  trap  is  supplied  with  steam  from  the 
boiler.  It  is  also  connected  with  the  boiler  by  the  pipe  P,  in  which 
is  a  check-valve  at  C.  Water  of  condensation  enters  the  trap  through 
the  pipe  E,  in  which  is  a  check-valve  H,  until  it  reaches  a  depth 
sufficient  to  raise  the  float  F,  which  opens  the  balanced  steam  valve  V, 


H 


Fig.  66.    Diagram  Illustrating  Operation  of  Return  Trap. 

called  an  equalizing  valve.  Steam  from  the  boiler  then  enters  the 
trap  and  equalizes  the  pressure.  Since  the  pressures  are  equal,  water 
in  the  trap,  because  of  its  height  above  the  water-level  of  the  boiler, 
will  flow  to  the  boiler  until  the  level  in  the  pipe  P  is  nearly  the  same  as 
the  water-level  in  the  boiler.  As  the  water-level  in  the  trap  falls,  the 
float  F  drops,  and  the  equalizing  valve  is  closed. 

In  some  forms  of  return  traps,  buckets  are  used  instead  of  floats. 

CALORIMETERS 

"Steam  from  a  boiler  is  generally  accompanied  with  more  or  less 
moisture.  This,  being  mechanically  suspended  in  the  steam,  cannot 
readily  be  measured  without  the  use  of  special  apparatus.  An  instru- 


BOILER  ACCESSORIES 


67 


ment  by  means  of  which  the  percentage  of  moisture  in  steam  can  be 
determined,  is  generally  called  a  calorimeter.  There  are  several  dif- 
ferent types  of  this  instrument,  only  three  of  which  will  be  described. 
The  Barrel  Calorimeter.  This  was  invented  by  the  distinguished 
engineer,  Mr.  G.  A.  Hirn,  and  is  not  only  one  of  the  earliest  of  these 
devices,  but  is  by  all  means  the  simplest  and  most  inexpensive  form 
of  calorimeter  in  practical  use.  It  is  shown  in  Fig.  67.  The  essential 
apparatus  consists  of  a  barrel  holding  about  400  Ibs.  of  water,  scales 
for  weighing — and  nothing  more.  A  pipe  with  suitable  connections 
leading  from  the  boiler  or  steam  main,  conveys  the  sample  of  steam 
to  be  tested.  This  pipe  should  be  provided  with  a  valve,  and  on  the 
end  should  be  a  piece  of  rubber  hose  which  can  readily  be  inserted  in 
the  barrel  or  removed. 
The  principle  of  this  calor- 
imeter is  extremely  simple. 
As  steam  flows  through  the 
pipe,  it  is  condensed  by  the 
water  in  the  barrel,  and  the 
increase  in  the  weight  of 
the  barrel  after  the  test  in- 
dicates the  total  amount  of 
moist  steam  condensed, 
while  the  rise  in  tempera- 
ture of  the  Water  in  the  Fig.  67.  Details  of  Barrel  Calorimeter. 

barrel  is  an  exact  measure  of  the  quantity  of  heat  obtained  from  this 
moist  steam. 

The  steam  tables  give  the  number  of  B.  T.  U.  in  dry  steam  and 
hot  water  at  various  temperatures  and  pressures;  and  with  this  data 
and  the  above-mentioned  observations  made  in  the  barrel,  the  per- 
centage of  steam  and  moisture  can  readily  be  determined. 

The  sampling  pipe  usually  projects  into  the  steam  main  a  few 
inches,  the  end  being  perforated  so  that  the  sample  will  be  drawn  from 
a  point  near  the  middle  of  the  pipe.  An  agitator  should  be  placed 
in  the  barrel,- so  that  the  water  may  be  thoroughly  stirred  and  a  uni- 
form temperature  maintained  during  the  test. 

To  test  a  sample  of  steam  by  this  method,  fill  the  barrel  about 
two-thirds  full  of  cold  water;  place  it  on  platform  scales,  and  carefully 
note  its  weight  and  temperature.  The  weight  of  the  barrel  and 


68  BOILER  ACCESSORIES 

fittings,  when  empty,  should  of  course  be  known,  so  that  the  weight 
of  the  water  alone  can  be  determined.  With  the  hose  removed  from 
the  barrel,  allow  steam  to  blow  through  the  pipe  until  it  has  become 
thoroughly  heated  If  the  sampling  pipe  is  long,  it  should  be  wrapped 
with  hair  felt  or  some  form  of  lagging,  to  prevent  condensation  during 
the  test.  As  soon  as  the  pipe  line  has  become  thoroughly  heated, 
plunge  the  hose  into  the  barrel  and  allow  the  steam  to  blow  through 
the  water  until  it  has  become  well  heated.  Shut  off  the  steam,  and 
carefully  note  the  weight  and  temperature. 

Suppose  W  =  Final  weight  of  water  in  barrel; 

w  =  Weight  of  cold,  condensing  water  before  steam  is  turned  on; 
ti  =  Temperature  of  the  cold  water; 
/2  =  Temperature  of  the  hot  water; 

P  ==  Absolute  pressure  of  steam  in  steam  pipe  (gauge  pressure  + 
atmospheric  pressure), 

From  the  steam  tables  in  the  back  of  the  book  may  be  found : 

q,  the  B.  T.  U.  in  one  pound  of  the  liquid  contents  of  the  moist  steam; 
qiy  the  B.  T.  U.  in  one  pound  of  the  cooling  water,  before  the  steam  was 

added; 
g2,  the  B.  T   U.  in  one  pound  of  this  water  after  the  steam  has  been 

added ; 
r,   the  heat  of  vaporization  corresponding  to  the  absolute  pressure — i  e., 

B.  T.  U.  given  up  by  one  pound  of  steam  condensed  into  water. 

If  x  equals  the  percentage  of  dry  steam  contained  in  the  supply 
pipe,  1  —  x  will  represent  the  amount  of  priming. 

x  (W  —  w)  =  the  total  amount  of  dry  steam  condensed ; 

(1  —  x)  (W  —  w)  =  the  total  amount  of  moisture  brought  into 
the  barrel  by  the  moist  steam. 

If  ql  equals  the  heat  in  one  pound  of  cooling  water,  then  q^w  will 
equal  the  total  heat  in  the  barrel  at  the  beginning. 

For  the  same  reason  q2W  will  equal  the  total  heat  after  the  steam 
has  been  condensed,  and  q2  W  -  qlw  will  equal  the  total  amount  of 
heat  gained  by  the  water  in  the  barrel. 

If  r  is  the  heat  of  vaporization,  then  r  x  (W-  w)  will  equal  the 
B.  T.  U.  contained  in  the  dry  steam;  and  if  q  is  the  heat  of  the  liquid 
corresponding  to  the  same  pressure,  then  q  (1  -  x)  (W  -  w)  will  equal 
the  B.  T.  U.  contained  in  the  moisture  brought  over  by  the  steam. 
It  is  apparent  that  the  sum  of  these  two  quantities  will  be  the  total 
number  of  B.  T.  U.  brought  from  the  steam  main  to  the  water  barrel, 
and  must  be  equal  to  q'2  W  -  q^  w,  the  heat  gained  by  the  water  in  the 


BOILER  ACCESSORIES  69 

barrel.  The  solution  of  this  equation  will  result  in  a  formula  which 
will  save  some  mathematical  computations. 

That  the  method  may  be  perfectly  clear,  let  us  first  consider  a 
numerical  example  in  full. 

Suppose   w  =  455  Ibs. 
W  =  495  Ibs. 

ti  =  50°  F. 

h  =  140°  F. 
P  =  75  Ibs. 

q  (from  steam  tables)  =  276.9 
0i     '"         "  "        =  18.1 

g2      "         "  "        =  108.2 

Then  the  total  heat  in  the  barrel  after  condensation,  is  equal 
to  (495  X  108.2)  =  53,559  B.  T.  U. 

The  total  heat  before  condensation  was  equal  to  455  X  18.1  = 
8,235  B.  T.  U.     Therefore  the  heat  brought  over  by  the  moist  steam 
will  be  53,559  -  8,235  =  45,324  B.  T.  U. 
Now,  from  the  steam  tables 

q  =  276.9;  and  r  =  898.8.     * 

The  heat  given  up  by  condensation   of  the  dry  steam  will  then  be 
898.8  X  (495- 455)* =  40*  X  898.8  =  35,952*;  and  the  heat  of  the 
liquid  in    the  moisture"  and  condensed  steam  will  be  40  X  276 . 9  = 
11,076,  making  the  total  heat  in  the  moist  steam  =  11,076  +  35,952*. 
Therefore,  11,076  +  35,952*  =  45,324 
35,952*  =  34,248 
x=  0.952 

That  is,  every  pound  of  moist  steam  contains  .952  Ib.  dry  steam  and 
.  048  Ib.  moisture ;  or  we  may  say  there  was  4 . 8  per  cent  of  priming. 
The  formula  may  be  derived  by  the  following  algebraic  work: 

Total  heat  in  bbl.  after  condensation  =  W  q2; 

Total  heat  in  bbl.  before  condensation  =  w  ql ; 

Total  heat  brought  over  by  steam  =  W  </,  —  w  ql ; 

Heat  of  liquid  in  condensed  steam  =  (W  —  w)  </; 

Latent  heat  in  dry  steam  =  x  (W  —  w)  r; 

Total  heat  in  moist  steam  =  x  (W  —  w)  r  +  (W  —  w)  q. 

Therefore, 

x  (W—  w)  r  +  (W  —  w )  q  =  W  q2  —  w  q^ 
xr  (W—  w)  =  W  q2  —  w  qL  —  W  q  +  w  q; 

or,  transposing  to  a  more  convenient  form, 


70 


BOILER  ACCESSORIES 


= 


r  (W-w) 

The  use  of  this  form  of  apparatus  is"  not  especially  to  be  com- 
mended, for  it  is  liable  to  error,  and  a  slight  discrepancy  in  the  weights 
or  the  temperatures  may  cause  a  large  error  in  the  result.  In  the 
above  calculations,  no  allowance  is  made  for  loss  of  heat  through 
radiation. 

Separator  Calorimeter.  This  instrument  shown  in  Fig.  68, 
consists  of  a  chamber  A,  into  which  is  led 
a  steam  pipe  D,  bringing  a  sample  of 
steam  from  the  boiler  kor  steam  main. 
This  pipe  leads  into  an  enlargement  per- 
forated with  small  holes,  or  into  a  cham- 
ber A  as  shown  in  Fig.  68.  The  calori- 
meter separates  the  moisture  from  the 
steam  just  as  a  steam  separator  does; 
and  the  exhaust,  which  is  dry  steam, 
passes  out  of  the  pipe  ,  wherein  is  in- 
serted a  diaphragm  containing  small  ori- 
fices, by  means  of  which  the  quantity  of 
steam  flowing  out  can  be  calculated  by 
thermodynamic  methods.  The  exhaust 
steam  can,  of  course,  be  led  to  some 
form  of  condensing  apparatus,  and  the 
condensation  weighed,  if  desired. 

As  the  steam  enters  the  calorimeter,  the 
moisture  is  drawn  toward  the  bottom  of 
the  chamber.  The  amount  of  water 
collected  can  readily  be  read  from  the 
gauge-glass  at  the  side,  to  which  a  gradu- 
ated scale  should  be  attached. 
Fig.  es.  separator  calorimeter.  The  amount  of  moisture  contained  in 

the  steam   can   be   weighed  directly  by 

drawing  it  out  of  the  gauge-cock  E.  The  amount  of  dry 
steam  is  measured  by  its  flow  through  the  orifices,  or  by  conden- 
sation.* If  W  =  weight  of  steam  discharged  -from  the  calorimeter, 

*NOTE:  For  principles  governing  flow  of  steam  through,  an.  orifice,  consult  any 
treatise  on  Thermodynamics. 


BOILER  ACCESSORIES 


71 


and  w  =  weight  of  water  collected,  then  the  percentage  of  priming 

will  be  fjT— 

W  +  w 

If  only  a  small  quantity  of  steam  is  used,  an  allowance  must  be 
made  for  condensation;  but  if  the  instrument  is  well  lagged  with 
hair  felt  or  other  suitable  material,  and  a  sufficient  quantity  of  steam 
is  used,  the  error  from  radiation  may  be  neglected.  Steam  should  be 
allowed  to  flow  pressureiTlCalort  pressure  inStearnR 

through  the  instru-  MainSteamPipe 

ment  until  it  has 
become  thoroughly 
heated,  before  be- 
ginning the  test. 

Throttling  Cal= 
o  r  i  m  e  t  e  r.  This 
was  invented  b  y 
Prof.  Cecil  H.  Pea- 
body,  and  is  made 
with  varying  con- 
structive details. 
Fig.  69  shows  the 
general  arrange- 
ment. The  mix- 
ture of  steam  and  • 
water  from  the 
boiler  is  taken  from 
the  main  steam 

,,  ,        ,  Fig.  69.    General  Arrangement  of  Throttling  Calorimeter. 

pipe  through  what 

is  termed  a  sampling  pipe.  Various  forms  of  this  pipe  are  made;  one 
arrangement  consists  of  a  pipe  closed  at  its  inner  end,  but  having 
numerous  holes  J  inch  in  diameter  drilled  staggering  around  the  sides. 
The  calorimeter  should  be  placed  as  close  as  possible  to  the  main 
steam  pipe;  and  the  gauge  for  indicating  the  pressure  in  the  main 
steam  pipe  should  be  placed  on  the  latter  and  near  the  calorimeter. 
The  gauge  is  sometimes  connected  to  a  tee  on  the  pipe  leading  to  the 
calorimeter;  but  it  is  better  to  have  this  gauge  where  the  velocity  of 
the  flowing  steam  is  less.  A  valve  is  placed  in  the  pipe  to  the  calori- 
meter, below  which  is  inserted  a  nipple  A  having  a  small  converging 


Sampling  Pipe 


fGas  Pipe 
Globe  Valve 


72  BOILER  ACCESSORIES 

orifice  D,  about  two-tenths  of  an  inch  in  diameter  and  very  carefully 
made.  The  object  of  such  an  orifice  is  to  determine  the  weight  of 
steam  flowing  through  the  calorimeter,  so  that  an  allowance  can  be 
made  for  the  loss  when  testing  an  engine  or  boiler,  where  the  net 
weight  used  is  required.  A  cup  B  is  screwed  into  the  top,  for  holding 
an  accurate  thermometer.  The  cup  is  made  of  brass,  and  is  filled  with 
oil;  but  if  mercury  is  used,  the  cup  must  be  of  iron  or  steel.  A  deli- 
cate gauge  C,  for  determining  the  pressure  in  the  calorimeter,  and  a 
pipe  and  valves  at  the  bottom,  complete  the  apparatus.  The  valve  N 
is  sometimes  omitted,  and  a  simple  pipe  used,  as  the  throttling  is  best 
accomplished  by  use  of  the  valve  E  or  orifice  D.  All  pipes  leading  to 
the  calorimeter  should  be  well  covered  with  a  good  non-conductor. 

To  use  the  instrument,  proceed  as  follows :  Open  wide  valves  E 
and  N,  to  bring  the  apparatus  to  a  uniform  temperature;  then  gradu- 
ally close  E  until  the  steam  in  the  calorimeter  is  superheated ;  that  is, 
until  the  temperature  as  shown  by  the  thermometer  is  greater  than  that 
corresponding  to  the  absolute  pressure  determined  from  the  reading 
of  the  gauge  C  and  barometric  pressure.  The  result  may  now  be 
calculated  as  follows : 

x  =  Weight  of  steam  contained  in  one  pound  of  the  mixture  from 
the  main  steam  pipe  or  other  source; 

\  =  Total  heat  corresponding  to  the  absolute  pressure  determined 
from  the  reading  of  the  gauge  (7  and  barometric  pressure;  * 

T  =  Temperature  as  shown  by  the  thermometer; 

tc  =  Temperature  of  steam  corresponding  to  the  absolute  pressure 
as  determined  by  the  reading  of  the  gauge  C  and  barometric  pressure; 

qs  =  Heat  of  the  liquid  corresponding  to  the  absolute  pressure 
in  the  steam  pipe; 

rs  =  Heat  of  evaporation  corresponding  to  the  absolute  pressure 
in  the  steam  pipe ; 

0 . 48  =  Heat  required  to  superheat  the  steam  one  degree  Fahren- 
heit under  constant  pressure. 

Total  heat  in  1  Ib.  superheated  steam  in  calorimeter  =  \  + 
0.48  (T-OB.T.  U. 

Total  heat  in  1  Ib.  moist  steam  in  steam  main  =  xra  -f  qa  B.  T.  U. 

These  two  quantities  are  equal ;  and  x,  being  the  only  unknown 
quantity,  the  equation  can  easily  be  solved. 

*NOTB:  Some  steam  tables  use  //instead  of  the  Greek  letter  A  (lambda). 


H 

lib 

s 


IS 

1 


BOILER  ACCESSORIES 


73 


x  , 


n 


Example.  Barometric  pressure,  14.78  Ibs.  ,  Absolute  pressure 
in  main  steam  pipe,  87.78  Ibs.  Absolute  pressure  in  calorimeter, 
23.03  Ibs.  Temperature  (T)  =  260°  F.  Then, 

Xc=  1,153.68  qa  =  288.1 

4  =  235.28  rs  =  890.88 

1,153  .  68  +  .  48  (260  -  235  .  28)  -  288  .  1 
x  =  -  n—  -  0-984  pound. 


Or,  in  other  words,  98.4  per  cent  of  the  mixture  is  steam;  or  the 
moisture  =  1  —0.984  =  0.016,  or  1.6  per  cent. 

This  form  of  calorimeter  is  suitable  only  for  cases  where  the 
moisture  does  not  exceed  three  per  cent  of  the  mixture.  Its  principle 
is  based  upon  the  assumption  that  there  is  no  loss  of  heat,  in  which 
case  steam  mixed  with  a  small  amount  of  water  is  superheated  when 
the  pressure  is  reduced  by  throttling. 

PIPING 

Although  piping  can  hardly  be  considered  a  boiler  accessory, 
a  few  general  remarks  will  not  be  out  of  place. 

Pipes  must  not  only  be  of  sufficient  size  and  strength,  but  should 
be  so  installed  as  to  make  —  •  — 

ample  provision  for  expansion  (Jfy 

due  to  the  high  temperature  f* 
when     they    are    filled    with  A 
steam.    The  supports  for  long 
pipe  lines  should  be  arranged 
somewhat  as  shown  in  Fig.  70, 
which  allows  the  pipe  a  con- 
siderable   amount    of    lateral 


Fig.  70.    Side  and  Transverse  Sectional  Views 

Showing  Methods  of  Arranging  Supports 

for  Long  Pipe  Lines. 


motion. 

If  the  pipe  line  is  long, 
an  expansion  joint  must  be 
provided.  Sometimes  a  curved 
U-bend  may  be  inserted  in  the  pipe  line,  which  of  itself  will  have 
flexibility  enough  to  provide  for  reasonable  expansion.  Or,  if  the 
steam  main  is  not  all  in  one  line,  a  similar  bend  may  be  pro- 
vided, with  elbows  and  nipples,  as  shown  in  Fig.  71.  In  this 


74 


BOILER  ACCESSORIES 


case,  any  expansion  of  the  steam  main  will  cause  the  nipples  to  turn 
slightly  in  "the  elbows.  This  motion,  of  course,  is  slight,  but  it  is 
sufficient  to  prevent  rupture.  U-bends  and  swivel-joints  are  hardly 
practicable  in  large  pipe ;  and  in  such  cases  a  slip-joint,  made  tight  by 
a  stuffing  gland,  is  usually  provided.  If  this  is  done,  great  care  must 
be  taken  that  the  steam-  main  is  straight  and  in  perfect  alignment,  as 
the  pipe  may  otherwise  bind  in  the  expansion  joint  and  cause  much 
damage  from  leakage. 

In  marine  work,  especial  care  must  be  taken  that  the  pipe  lines 
are  not  so  rigidly  connected  together  that  they  will  be  injured  by  the 
working  of  the  ship.  This  can  readily  be  provided  for  by  laying 
the  pipe  in  such  a  way  as  to  provide  a  simple  form  of  swivel-joint. 

,^  The  pipe  lines  should  be  as 

frj  IB 

straight  as  possible,  to  prevent 
unnecessary  friction  of  the 
steam  and  unnecessary  con- 
densation; and  they  should,  if 
possible,  be  so  installed  as  to 
leave  no  pockets  wherein  con- 
densation may  collect.  If  such 
a  pocket  is  unavoidable,  a 

drain  must  be  provided,  lead- 
»  ,,  , 
mg    from    the     pocket    to    the 

steam  trap,  whence  the  con- 
densation may  be  discharged  into  the  hot  well  or  filter-box,  because 
the  collection  of  water  in  steam  pipes  is  a  source  of  inconvenience 
and  danger. 

The  pipe  lines  should  be  installed  with  sufficient  slope,  so  that 
the  condensation  will  readily  drain  to  a  convenient  point  whence  it 
may  be  drawn  off.  This  slope  should  be  in  the  direction  of  the  flow 
of  the  steam,  as  the  water  will  not  readily  flow  otherwise.  Great 
care  should  be  taken  that  the  pipe  lines  nowhere  sag,  as  such  a  de- 
pression will  collect  condensation.  This  may  cause  very  little  dis- 
turbance unless  the  pressure  of  the  steam  is  suddenly  raised,  in  which 
case  the  water  is  liable  to  flow  bodily  along  the  pipe;  and  if  it  does 
not  enter  the  cylinder  of  the  engine  and  cause  damage  there,  it  will 
cause  a  serious  water-hammer  which  may  rupture  the  elbows  of  the 
pipe  and  may  endanger  life. 


ELEVATION 

Fig  71.    Method  of  Forming  Swivel-Joint  in 
Steam  Piping  to  Counteract  Effects  of 
Expansion  and  Contraction. 


BOILER  ACCESSORIES  75 

Formerly,  when  low  pressures  were  used,  cast  iron  was  a  common 
material  for  a  main  steam  pipe  leading  from  the  boiler  to  the  engine, 
but  the  higher  pressures  of  to-day  require  the  best  wrought  iron  or 
steel.  In  marine  work,  copper  is  commonly  used;  but  with  the 
advent  of  higher  and  higher  pressures,  copper  fails  to  give  the 
requisite  strength,  and  it  has  to  be'  reinforced  with  wire  or  iron 
bands.  At  pressures  not  over  150  Ibs.,  copper  pipes  may  be  used,  by 
the  British  Board  of  Trade  rules,  15  inches  in  diameter;  but  at  200 
Ibs.,  copper  pipes  are  not  allowed  over  10  inches  in  diameter.  For 
large  sizes,  riveted  iron  or  steel  pipe  may  be  used.  For  high  pres- 
sures, cast-steel  fittings  are  required  by  the  U.  S.  Steamboat  Inspec- 
tion rules.  There  was  always  danger  that  the  large  copper  pipe  would 
burst;  and  it  is  now  the  common  practice  to  use  steel  for  such 
purposes. 

Large  steam  pipe  is  made  in  sections  which  can  be  riveted  to- 
gether. The  small  sizes  are  fitted  with  the  ordinary  type  of  flange,  and 
the  sections  may  be  bolted  together,  a  suitable  gasket  being  used 
between  the  two  flanges  to  make  a  steam-tight  joint.  The  flanges  are 
machined  perfectly  smooth,  and  the  packing  may  consist  of  rubber  and 
fiber  reinforced  with  wire  insertion,  or  of  asbestos,  or  of  corrugated 
copper. 

The  true  inside  diameter  of  steam,  gas,  or  water  pipe  is  not  always 
the  same  as  the  size  of  the  pipe  as  popularly  known.  For  instance, 
what  is  called  "3-inch"  pipe  has  an  actual  inside  diameter  of  3.067 
inches,  and  3 . 5  inches  outside  diameter.  The  actual  sizes  of  pipe, 
inside  and  outside,  can  be  found  in  any  handbook  or  steamfitter's 
catalogue. 

LAGGING 

When  steam  pipes  are  exposed  to  the  air,  a  considerable  amount 
of  condensation  will  collect  in  them,  depending  on  the  condition  of 
the  surface  of  the  pipe,  on  the  difference  in  temperature  between  the 
steam  and  the  surrounding  air,  and  on  the  velocity  of  the  steam 
through  the  pipe.  This  condensation  will  cause  a  large  amount  of 
heat  to  be  lost  to  useful  work,  and  will  make  the  dangers  of  water- 
hammer  possible  unless  carefully  drained.  Tests  have  shown  that 
about  2  B.  T.  U.  are  lost  per  square  foot  of  pipe  per  hour  per  degree 


76  BOILER  ACCESSORIES 

of  difference  in  temperature.  While  the  loss  for  a  few  hours  is  not 
likely  to  be  great,  yet,  if  taken  for  an  entire  year  throughout  a  con- 
siderable length  of  pipe,  the  sum  total  will  be  very  large  indeed.  The 
following  table  gives  some  idea  of  the  loss  of  heat  through  bare  pipe  at 
200  Ibs.  pressure : 

HEAT  LOSSES  IN  BARE  PIPES 

B.  T.  U.  Loss 
•    .  }     PER  SQ.  FT. 
CONDITION  OF  PIPE  PER  MINUTE 

New  Pipe .' 11.96 

Painted  Glossy  Black . 12.10 

Painted  Glossy  White 12  .02 

Fair  Condition 13 .84 

Rusty 14.20 

Coated  with  Cylinder  Oil 13 .90 

Painted  Dull  Black 14  .40 

VARIATION  OF  HEAT  LOSS  WITH  PRESSURE 

HEAT  Loss 
B.  T.  U.  PER  SQ. 
PRESSURE  FT.  PER  MINUTE 

340 '. 15  .97 

200 13.84 

100 8  .92 

80 8.04 

60 : 7.00 

40 5.74 

A  full  account  of  some  interesting  tests  can  be  found  in  a  paper 
entitled  Protection  of  Steam-Heating  Surfaces,  by  C.  L.  Norton,  Vol.  XIX, 
Proceedings  of  the  American  Society  of  Mechanical  Engineers,  1898,  from 
which  these  tables  have  been  taken. 

Pipe  Coverings.  To  make  this  loss  from  radiation  as  small  as 
possible,  it  is  customary  to  cover  the  pipe  or  boiler  with  some  material 
which  will  prevent  loss  of  heat  and  which  will  not  burn.  There  is 
considerable  difference  in  the  value  of  various  substances  as  preventa- 
tives  of  heat  radiation.  Their  value  varies  nearly  in  an  inverse  ratio 
to  their  conducting  power;  but  due  allowance  must  be  made  for  the 
possible  deterioration  of  the  pipe  covering.  The  following  table  gives 
the  relative  value  of  various  substances  with  reference  to  their  ability 
to  prevent  radiation  of  heat.  For  purposes  of  comparison,  the  value 
cf  wool  is  taken  as  the  standard : 


BOILER  ACCESSORIES  77 

RELATIVE  VALUES  OF  VARIOUS  PREVENTATIVES  OF 
RADIATION  OF  HEAT 

Felt,  Hair,  or  Wool 100 

Asbestos  Sponge 98 

Air-Cell  Asbestos 89 

Mineral  Wool 68-83 

Carbonate  of  Magnesia 67  —  76 

Charcoal 63 

Sawdust 61  —  68 

Asbestos  Paper 47 

Wood 40-55 

Asbestos,  Fibrous 36 

Plaster  of  Paris 34 

Air  Space  (Undivided) 22 

There  are  many  patented  coverings  which  are  very  efficient,  but 
they  are  too  numerous  even  to  mention.  The  above-mentioned  article 
from  the  Proceedings  of  the  American  Society  of  Mechanical  Engineers 
gives  the  results  of  tests  of  several  of  these  coverings.  A  good  pro- 
tection is  afforded  by  air  confined  in  minute  cells,  such  as  is  to  be  had 
in  the  air-cell  asbestos  board;  this  is  made  by  cementing  together 
several  layers  of  asbestos  paper  which  have  been  corrugated  or  in- 
dented by  machinery  so  as  to  form  minute  air-cells.  The  more 
minute  the  subdivision  of  these  cells,  the  better  the  protection  is  likely 
to  be.  Hair  felt  is  one  of  the  most  efficient  non-conductors,  because  it 
is  very  porous  and  contains  a  large  number  of  air-cells.  It  is  not  one 
of  the  best  coverings,  however,  because  it  is  liable  to  deteriorate,  and 
its  life  on  high-pressure  pipes  is  not  likely  to  be  more  than  four  or  five 
years.  On  low-pressure  work  it  may  last  for  a  considerably  longer 
time. 

Mineral  wool,  a  fibrous  material  made  from  blast-furnace  slag, 
is  an  efficient  and  noncombustible  covering,  but  is  brittle  and  liable 
to  fall  off. 

The  coverings  most  easily  applied  to  pipes  are  those  applied  in 
sectional  form,  which  clasp  around  the  pipe  and  are  fastened  by  brass 
bands  at  convenient  intervals.  Such  coverings  are  made  both  of 
asbestos  and  of  magnesia,  and  are  usually  of  about  1  inch  in 
thickness. 

A  good,  cheap  covering  can  be  made  by  wrapping  several  layers 
of  asbestos  paper  around  the  pipe,  and  then  covering  these  layers  with 
a  layer  of  hair  felt  perhaps  f  inch  thick,  the  whole  being  wrapped  in 


78  BOILER  ACCESSORIES 

canvas.  On  low-pressure  steam  pipes  this  covering  will  last  ten  to 
fifteen  years. 

Cork  is  perhaps  one  of  the  most  satisfactory  coverings  from  the 
point  of  radiation  loss,  but  is  rather  more  expensive  than  asbestos  or 
magnesia. 

It  has  generally  been  the  impression  that  it  is  not  economical 
to  cover  a  pipe  to  more  than  one  inch  in  thickness.  This  will  depend 
upon  the  cost  of  the  covering  and  the  length  of  time  it  is  likely  to  last. 
If  it  does  not  last  more  than  five  years,  one  inch  is  probably  the  most 
economical  thickness;  but  if  the  life  of  the  covering  is  likely  to  be 
ten  years  or  more,  a  second  inch  in  thickness  can  be  applied  to  advan- 
tage. For  instance,  in  the  above-mentioned  tests,  in  the  case  of  " Non- 
pareil cork,"  increasing  the  thickness  from  one  to  two  inches  raised  the 
cost  from  $25  to  $30  per  100  square  feet,  and  increased  the  net  saving 
in  five  years  by  $10,  and  by  $30  in  ten  years.  A  third  inch  of  covering 
did  not  produce  saving  enough  to  pay  for  its  cost.  In  each  case  with 
the  asbestos  fire-board,  a  second  inch  in  thickness  showed  a  saving 
of  $20  in  ten  years,  while  the  third  inch  in  thickness  showed  an 
actual  loss  from  the  dollars-and-cents  point  of  view.  It  would  be 
well  to  remark  that  it  is  of  great  importance  that  the  pipe  covering 
should  be  kept  in  repair,  for  a  loose-fitting  covering  is  of  little  value. 

Boiler  Coverings.  Much  the  same  remarks  may  be  made  with 
regard  to  boiler  covering  as  have  been  made  with  regard  to  pipe 
covering,  except  that  the  covering  put  on  boilers  is  usually  somewhat 
less  efficient  and  is  applied  in  greater  thickness.  Probably  one  of  the 
best  coverings  for  a  marine  boiler — or,  in  fact,  for  any  internally- 
fired  boiler — is  a  layer  of  air-cell  asbestos  board,  covered  with  a  coating 
perhaps  two  inches  thick  of  magnesia  or  asbestos.  This  comes  in 
powder  form,  and  when  mixed  with  water  can  be  readily  applied  with 
a  trowel.  Coverings  on  boilers  are  best  placed  directly  against  the 
shell  without  an  air-space,  so  that  any  leak  in  a  joint  or  rivet  will  reveal 
the  spot  by  moistening  the  covering;  otherwise  the  escaping  water  may 
run  down  through  the  air-space  and  appear  at  some  remote  point,  the 
leak  thus  being  difficult  to  locate. 

An  efficient  covering  for  boilers  is  made  of  either  magnesia  or 
asbestos  in  the  form  of  blocks  of  the  proper  curvature,  which  can  lie 
directly  against  the  boiler;  but  this  form  of  covering  is  rather  more 
expensive  than  the  asbestos  or  magnesia  cement.  To  secure  an  extra 


BOILER  ACCESSORIES  79 

hard  finish  a  coating  of  plaster  of  Paris  may  be  put  on  outside  the 
magnesia  or  asbestos.  No  boiler  or  pipe  covering  should  contain 
sulphate  of  lime,  as  this  is  liable  to  cause  corrosion. 

If  an  internally-fired  boiler  is  properly  lagged,  there  is  little  danger 
that  any  large  amount  of  heat  will  be  lost,  as  the  heat  of  the  fire  must 
pass  through  the  water  before  radiating.  This  is  not  true  with  an 
externally-fired  boiler,  where  a  considerable  amount  of  heat  may 
radiate  through  the  brick  setting  of  the  boiler  without  coming  in 
contact  with  the  boiler  at  all.  The  setting  of  such  a  boiler  should 
be  arranged  with  properly  confined  air-spaces;  a1  id  an  efficient  pro- 
tection from  the  radiation  of  heat  at  the  top  of  the  boiler  may  be  had 
by  allowing  a  slight  space  between  the  boiler  and  the  top  covering 
for  the  circulation  of  the  hot  gases  of  combustion.  These  are  on  their 
way  to  the  chimney;  and  as  they  are  necessarily  hotter  than  the  water 
in  the  boiler,  they  prevent  radiation  at  this  point. 

HORSE-POWER  OF  BOILERS 

The  unit  which  we  call  the  horse-power  is  arbitrary.  Assuming 
that  30  pounds  of  steam  are  required  per  horse-power  per  hour  for 
an  average  engine,  this  unit  for  boilers  has  been  adopted. 

One  (1)  horse-power  is  the  evaporation  of  30  pounds  of  water 
per  hour,  from  a  temperature  of  100°  F.  into  steam  at  70  pounds  gauge 
pressure.  This  is  considered  equivalent  to  the  evaporation  of  34  \ 
pounds  per  hour  from  and  at  212°  F.  A  boiler  horse-power  is  equiv- 
alent to  33,327  B.  T.  U.  per  hour. 

As  all  boilers  do  not  generate  steam  at  the  same  pressure  and 
from  the  same  temperature  of  feed-water,  it  is  necessary  to  reduce  the 
actual  evaporation  to  an  equivalent  evaporation.  Unless  this  is  done, 
the  relative  performances  of  boilers  cannot  be  compared. 

For  this  comparison,  the  actual  evaporation  is  reduced  to  the 
equivalent  evaporation  from  and  at  212°  F.     That  is,  we  suppose 
the  water  to  be  fed  at  212°  and  evaporated  into  steam  at  212°. 
Let  W  —  Water  actually  evaporated  in  pounds; 

H  =  Total  heat  of  steam  above  32°  F.,  at  factual  absolute  pres- 
sure; 

T  =  Temperature  of  feed  water; 

w  =  Equivalent  evaporation  from  and  at  212°  F. 

Since  966  B.  T.  U.  are  necessary  to  evaporate  one  pound  of  water 


80 


BOILER    ACCESSORIES 


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BOILER  ACCESSORIES  81 

from  and  at  212°  R,  the  equivalent  evaporation  may  be  found  from 
the  formula, 


W  (H  +  32  —  T)  =  966^,  or  w  = 


9oo 

Then  the  horse-power  of  the  boiler  is  : 

w 


H.P.  = 


34.5 
The  above  method  is  considerably  shortened  by  substituting  for 

TT       ,        OO   _    m 

the   quantity  -         —  -  --  >  the  number  found  in  the  accompanying 


table  (page  80)  which  corresponds  to  the  actual  feed-water  tempera- 
ture and  steam  pressure. 

For  example,  a  boiler  is  required  to  furnish  2,100  pounds  of 
steam  per  hour.  If  the  gauge  pressure  is  85  pounds,  and  the  feed- 
water  enters  at  50°  F.,  what  is  the  equivalent  evaporation,  and  what 
is  the  horse-power? 

From  the  table,  the  factor  for  85  pounds  pressure  and  50°  F.  is 
1.204.  Then  the  equivalent  evaporation  would  be  1.204  X  2,100  = 

2,528.4  pounds;  and  2>528'4,  =  73  (approx.)  =  the  H.  P. 
o4.5 


CORROSION  AND  INCRUSTATION 

There  are  several  causes  which  tend  to  shorten  and  destroy  the 
life  of  every  boiler.  These  may  be  divided  into  two  general  classes, 
chemical  and  mechanical,  and  are  usually  the  result  of  improper  feed- 
water  or  of  improper  care.  Pure  water,  free  from  air  and  carbon 
dioxide,  has  no  evil  effect  on  the  iron;  but  all  natural  waters,  whether 
from  rain,  lake,  river,  or  sea,  contain  air  and  a  little  carbon  dioxide  in 
solution,  and  such  water  will  cause  iron  to  corrode,  even  though  no 
other  impurities  are  present. 

Sea  water,  heated  under  a  steam  pressure  of  30  Ibs.,  even  if  it 
contains  no  air,  will  liberate  a  small  amount  of  hydrochloric  acid, 
which  instantly  attacks  the  iron  of  the  boiler  unless  counteracted  by 
some  chemical  agent. 

External  Corrosion.  There  are  two  forms  of  corrosion,  external 
and  internal.  External  may  be  due  to  faulty  setting,  to  improper  care, 
or  to  moisture  from  external  sources  or  from  leakage  from  joints  and 


82  BOILER  ACCESSORIES 

valves.  A  large  amount  of  external  corrosion  is  the  result  of  setting 
boilers  in  a  mass  of  brickwork,  which  readily  absorbs  moisture,  and 
which,  when  not  under  fire,  is  likely  to  keep  the  boiler-plates  damp. 
The  exterior  of  a  boiler  encased  in  brickwork,  moreover,  is  not  so 
easily  accessible,  and  a  considerable  amount  of  deterioration  may  take 
place  without  being  readily  detected.  The  leakage  from  a  joint,  al- 
though slight,  may,  if  long  continued,  badly  corrode  the  boiler. 

Internally-fired  boilers  are  supported  on  saddles  and  are  easily 
accessible;  and  the  magnesia  or  asbestos  lagging  with  which  they  are 
usually  covered  will  tend  to  absorb  a  certain  amount  of  moisture, which 
will  be  given  off  when  hot,  thus  helping  to  keep  the  boiler  dry.  If  a 
leak  occurs  of  appreciable  size,  the  covering  will  become  softened  and 
its  presence  will  be  detected  at  once,  and  repairs  can  be  made  before 
any  serious  damage  is  done.  The  exterior  of  an  internally-fired 
boiler,  being  at  all  times  accessible,  can  be  properly  taken  care  of, 
which  is  not  true  of  a  boiler  set  in  brickwork.  Rivets  and  riveted 
joints  should  as  far  as  possible  be  kept  out  of  contact  with  the  fire. 

Internal  Corrosion.  This  is  the  result  of  the  chemical  action  of 
impure  feed-water.  It  may  occur  in  the  form  of  a  general  corrosion 
or  wasting-away  of  the  boiler-plates,  or  in  the  form  of  pitting  or 
grooving,  the  effects  of  which  are  likely  to  be  local.  Pitting  and 
general  corrosion  are  entirely  the  result  of  chemical  action,  while 
grooving  is  the  result  of  chemical  and  mechanical  action  combined. 

It  is  not  easy  to  discover  general  corrosion,  because  it  acts  more 
or  less  uniformly  over  a  large  surface.  Sometimes  the  rivet-heads 
rust  in  proportion  to  the  plates,  so  that  the  wasting-away  of  the  plates 
is  not  easily  noticeable.  A  uniform  corrosion  is  the  hardest  to  detect, 
and  can  usually  be  discovered  only  by  drilling  the  boiler  and  gauging 
the  thickness  of  the  plate.  If  the  thickness  of  the  plate  is  found  to  be 
materially  reduced,  the  working  pressure  of  the  boiler  should  be 
lowered  in  proportion. 

Sometimes  the  water  will  attack  the  plates  only  in  the  vicinity 
of  the  water-line,  in  some  instances  confining  the  damage  to  a  belt  0 
inches  or  8  inches  wide.  Sometimes  a  few  rivets  below  water-level 
will  be  corroded,  the  rest  remaining  in  a  comparatively  good  con- 
dition. Often  the  stays  are  weakened  more  rapidly  than  the  plates, 
and  the  screw-threads  of  a  stay  may  be  badly  corroded  while  the 
shank  of  the  stay  remains  uninjured. 


BOILER  ACCESSORIES  83 

Pitting.  Fatty  acids,  which  are  likely  to  come  over  in  the  feed- 
water  if  vegetable  oils  are  used  to  lubricate  the  cylinder,  are  especially 
active  in  the  production  of  small  pits  throughout  the  interior  of  the 
boi  ler.  Pitting  appears  in  the  form  of  small  holes  or  in  patches  from 
J  inch  to  1  inch  in  diameter,  or  even  as  irregularly  shaped  depressions. 
If  the  holes  are  small  and  close  together,  the  plate  is  said  to  be  honey- 
combed. It  is  generally  believed  that  this  phenomenon,  the  result  of 
chemical  action,  is  due  to  a  lack  of  homogeneity  in  the  material  of 
the  boiler,  although  an  entirely  satisfactory  explanation  has  not  yet 
been  given.  Pitting  may  also  be  caused  by  galvanic  action,  which 
may  take  place  especially  if  sea  water  is  used.  As  pitting  occurs 
when  there  is  no  cause  whatever  for  galvanic  action,  this  can  be  only 
a  secondary  cause  at  best.  It  is  reasonable  to  suppose  that  acids  will 
attack  the  most  susceptible  portions  of  the  plate;  and  if  there  is  any 
lack  of  homogeneity  in  the  icon,  it  is  probable  that  the  places  or  spots 
most  favorable  to  chemical  attack  will  suffer  first. 

Grooving.  Grooving  is  probably  the  result  of  straining,  springing, 
or  buckling  of  the  plates,  aided  by  local  corrosion  or  by  the  same  forces 
which  cause  pitting.  Straining  of  the  plates  may  be  due  to  insufficient 
or  improper  staying,  thus  causing  the  plates  to  spring  back  and  forth 
as  the  steam  pressure  varies.  This  phenomenon  is  most  commonly 
found  in  stationary  boilers  of  the  "Cornish"  or  "Lancashire"  types 
appearing  in  the  flat  end-plates  around  the  edge  of  the  angle  iron,  or 
in  the  root  of  the  angle  iron.  Too  rigid  staying  of  the  ends  by  gussets 
or  diagonal  stays,  or  too  great  a  difference  in  expansion  between  dif- 
ferent parts,  is  almost  sure  to  produce  grooves. 

Internal  grooving  may  be  caused  as  the  direct  result  of  excessive 
calking,  which,  by  injuring  the  surface  of  the  metal,  exposes  it  to  the 
corrosive  action  of  the  feed -water.  It  is  to  be  expected  that  if  strains 
which  cause  the  plates  to  come  and  go  are  set  up  in  the  boiler — 
especially  if  the  stresses  can  be  concentrated  along  a  definite  line — a 
weakness  will  be  developed  there,  and  it  will  be  a  susceptible  point 
for  chemical  attack.  Sometimes  grooving  is  so  fine  as  to  appear  to 
be  a  mere  crack.  But  the  crack,  although  perhaps  only  ^T  inch  in 
width,  may  extend  into  the  plate  for  a  considerable  depth.  Grooves 
are  not  readily  detected,  and  if  allowed  to  continue  for  any  length  of 
time  are  likely  to  produce  serious  results. 


84  BOILER  ACCESSORIES 

Prevention.  The  best  way  to  prevent  internal  corrosion  is  to 
use  water  that  has  no  corrosive  effect  on  the  plates.  If  internal  cor- 
rosion has  begun,  a  change  of  feed-water  may  prolong  the  life  of  the 
boiler,  but  in  many  instances  it  is  cheaper  to  build  a  new  boiler  than 
frequently  to  change  the  water  supply.  Sometimes  the  introduction 
of  a  thicker  jSlate  at  places  where  the  water  is  found  to  be  most  active 
will  be  advisable;  but,  as  these  plates  are  stronger  than  the  rest  of 
the  boiler,  the  strains  will  not  be  uniformly  distributed,  and  stresses 
are  likely  to  concentrate  along  the  edge  of  this  heavy  plate,  which  will 
be  a  susceptible  point  for  the  formation  of  grooves. 

The  acidity  of  the  feed-water  may  be  neutralized  by  some  alka- 
line substance,  such  as  soda,  before  it  enters  the  boiler.  The  amount 
of  soda  to  be  used  varies  with  the  acidity  of  the  water;  but  it  should 
always  be  used  in  the  smallest  possible  quantity,  as  the  soda  is  likely 
to  produce  priming  in  the  boiler  and  will  be  injurious  if  there  is  much 
salt  present.  Vegetable  oils  should  not  be  used  for  cylinder  lubri- 
cation if  the  condensation  is  to  be  fed  back  to  the  boiler,  as  such  oils 
contain  acids  which  will  always  produce  injurious  effects.  Mineral 
oils  alone  should  be  used. 

To  allow  for  a  general  corrosion,  T^  inch  to  T\  inch  extra  thick- 
ness of  shell  should  be  provided.  All  seams  of  a  boiler  should  be 
tight,  and  no  wrelded  tubes  should  be  used,  as  pitting  and  grooving 
are  likely  to  occur  in  the  vicinity  of  the  weld.  When  not  in  use,  no 
moist  air  should  be  allowed  in  the  boiler.  A  boiler  can  be  thoroughly 
dried  out  either  by  the  application  of  heat  or  by  placing  in  it  lime, 
which  will  readily  absorb  the  moisture. 

The  water  fed  to  the  boiler  should  be  thoroughly  filtered  to  re- 
move as  much  grease  as  possible,  for,  although  mineral  oil  is  not  likely 
to  cause  pitting,  it  has  a  serious  effect  in  the  formation  of  boiler  scale. 

Incrustation.  The  incrustation  formed  by  the  accumulation  of 
the  deposit  of  sediment  in  the  feed  water,  is  called  scale  or  sludge, 
The  solid  matter  in  the  feed-water  may  be  precipitated  by  the  rise 
in  temperature,  or  left  behind  as  the  result  of  the  evaporation  of  the 
water.  These  solids,  unless  blown  out,  are  liable  to  become  hardened 
on  the  inner  surface  of  the  boiler.  A  thin  coating  of  scale  in  itself 
is  beneficial,  for  it  keeps  the  water  from  direct  contact  with  the  iron, 
and  prevents  corrosion  and  pitting;  but  the  danger  is  that  if  a  thin 
scale  forms,  a  thicker  one  will  form,  and  this  heavy  scale,  being  a  poor 


BOILER  ACCESSORIES  85 

conductor  of  heat,  not  only  causes  considerable  waste  of  fuel,  but 
allows  the  plates  next  the  furnace  to  become  overheated,  with  the 
result  that  they  are  likely  to  give  way,  and  the  boiler  may  collapse. 

The  amount  of  solid  matter  in  solution  is  measured  in  grains  per 
U.  S.  gallon.  The  quantity  varies  greatly  in  waters  from  different 
sources,  but  is  seldom  over  40  grains  per  gallon.  It  is  not  the  quantity 
of  matter  in  solution,  but  its  nature,  that  determines  the  influence  of 
feed -water.  With  proper  attention  to  the  boiler,  the  presence  of  a 
certain  amount  of  carbonate  or  sulphate  of  soda  would  not  be  injurious ; 
while  the  same  number  of  grains  per  gallon  of  salts  of  lime  would 
cause  serious  trouble.  Salts  of  lime  (calcium),  together  with  car- 
bonate of  magnesia,  are  the  solids  most  frequently  found,  and  are  the 
most  troublesome.  Hard  water  contains  considerable  quantities  of 
lime.  So-called  soft  water  has  usually  but  little  solid  matter  in  sus- 
pension, but  it  may  contain  vegetable  or  organic  impurities  that  will 
cause  corrosion  or  pitting. 

The  oil  used  in  the  engine  is  likely  to  get  into  the  boiler  through 
the  feed-water,  if  it  is  not  carefully  filtered  or  passed  through  a  grease- 
extractor.  The  oil  is  likely  to  be  deposited  on  the  sides  and  tubes  of 
the  boiler,  and  not  only  is  a  poor  conductor  of  heat,  but,  mingling 
with  the  sediment  which  is  precipitated  from  the  hot  water,  pro- 
duces a  mixture  which  is  readily  baked  onto  the  boiler-plates  and  is 
especially  obstinate  and  difficult  to  remove.  There  are  efficient 
grease-extractors  now  on  the  market,  which  will  remove  practically 
every  trace  of  oil. 

Carbonate  of  Lime,  Carbonate  of  lime  is  held  in  solution  in  water 
by  an  excess  of  carbon  dioxide.  As  the  water  is  heated,  the  excess  of 
carbon  dioxide,  or  carbonic  acid,  is  driven  off,  and  the  carbonates  will 
be  precipitated  in  the  form  of  a  whitish  or  grayish  sediment  of  the 
consistency  of  mud.  If  these  precipitates  are  not  mixed  with  im- 
purities, they  may  be  washed  out  of  the  boiler  after  it  has  been  allowed 
to  cool;  but  if  there  is  oil,  organic  matter,  or  sulphate  of  lime,  the 
deposits  are  likely  to  become  hard.  They  may  readily  be  drawn  off 
through  the  bottom  blow-out;  but  if  there  is  much  pressure  in  the 
boiler,  the  blow-out  valve  should  be  opened  only  for  a  very  short  time. 
If  a  considerable  amount  of  water  js  blown  out  while  the  boiler  is  still 
very  hot,  a  large  part  of  this  precipitation  is  likely  to  be  baked  onto  the 
tubes  and  interior  of  the  boiler  in  a  manner  that  defies  removal.  Short 


86  BOILER  ACCESSORIES 

and  frequent  blowings  will  accomplish  the  desired  result;  for  while 
the  boiler  is  in  action  these  precipitates  are  more  or  less  in  motion,  and 
frequent  blowing  will  keep  the  boiler  clear.  Oil  and  various  organic 
matters  rising  to  the  surface  can  easily  be  removed  by  frequently 
opening  the  surface  blow-out. 

Sulphate  of  Lime.  This  troublesome  salt,  like  the  carbonate  of 
lime,  is  precipitated  with  a  rise  of  temperature;  and  at  280°  F.,  none 
is  left  in  solution.  This  sediment  is  likely  to  form  a  hard,  adhering 
scale ;  but  if  a  little  carbonate  of  soda,  or  soda  ash,  is  introduced  with 
the  feed  water,  calcium  carbonate  .is  precipitated  in  the  form  of  a 
white  powder  which  can  be  readily  washed  out.  The  carbonate  of 
soda  should  be  introduced  at  regular  intervals,  a  portion  of  it  being 
dissolved  in  water  which  can  be  mixed  with  the  feed  in  the  hot  well. 
As  little  soda  as  possible  should  be  used,  as  it  is  likely  to  cause  priming 
and  foaming.  The  hardness  of  the  scale  formed  by  the  sulphate  of 
lime  depends  on  the  other  impurities  in  the  water  and  on  the  tempera- 
ture ;  and  consequently  the  amount  of  soda  that  can  safely  be  used  can 
be  determined  only  by  trial.  Ammonium  chloride,  commonly  called 
sal-ammoniac,  is  sometimes  used  to  break  up  these  lime  compounds, 
but  is  not  always  desirable,  as  it  may  break  up  the  chlorides  if  other 
conditions  are  right,  thus  forming  free  chlorine,  which  attacks  the 
boiler. 

Carbonate  of  Magnesia  is  seldom  found  in  such  large  quantities 
as  calcium  salts.  Like  the  carbonate  of  lime,  it  is  precipitated  in  hot 
water.  If  there  is  any  oil  or  organic  matter  present,  it  is  likely  to 
form  an  injurious  precipitation. 

Iron  Salts  form  a  reddish  incrustation  which  is  very  injurious  to 
boiler-plates.  B  rakish  water  containing  chloride  of  magnesium  is 
also  injurious;  for,  when  heated,  the  chloride  decomposes,  forming 
magnesia  and  hydrochloric  acid,  the  latter  rapidly  corroding  iron. 

A  piece  of  thick  scale  broken  from  the  plates  of  the  boiler,  will 
show  a  series  of  layers  of  various  thickness,  some  of  them  crystalline 
and  some  amorphous.  Between  these  hard  layers  are  frequently 
found  layers  of  soft  or  earthy  matter. 

Nothing  definite  is  known  in  regard  to  the  loss  of  heat  caused  by 
scale  on  heating  surfaces,  for  there  are  too  many  circumstances  to  be 
considered  to  admit  of  exact  calculation.  It  has  been  stated  that  a 
layer  TY  inch  thick  in  the  tubes  of  multitubular  boilers,  is  equivalent 


BOILER  ACCESSORIES  87 

to  a  loss  of  from  15  to  20  per  cent  of  fuel.  The  loss  increases  rapidly 
with  the  thickness  of  the  scale.  A  uniform  coating  of  scale  is  not 
nearly  so  harmful  as  irregular  deposits,  for  in  the  latter  case  the  evil 
effects  of  overheating  are  likely  to  be  produced,  and  overheating  will 
result  where  it  is  least  suspected. 

Prevention.  Incrustation  may  be  prevented  by  precipitating  the 
scale-forming  substances  before  the  feed -water  reaches  the  boiler, 
by  the  introduction  of  chemical  compounds  to  neutralize  the  evil 
effects,  or  by  removing  the  sediment  before  it  becomes  hard.  Scale 
may,  of  course,  be  removed  by  hand  from  the  interior  of  the  boiler ;  but 
this  is  a  slow  and  tedious  process.  One  of  the  chief  objections  to 
removing  scale  by  hand  is  that  the  surfaces  of  the  boiler  are  likely  to 
become  abraded  by  the  chipping  tools,  and  this  offers  excellent  oppor- 
tunity for  pitting  and  local  corrosion  to  set  in. 

Scale  has  sometimes  been  removed  by  blowing  the  boiler  off  at 
comparatively  high  pressure,  and  then  filling  it  with  cold  water.  This 
causes  a  severe  contraction  of  the  plates,  and  is  likely  to  loosen  the 
scale;  but  it  will  at  the  same  time  cause  serious  injury  to  the  boiler, 
and  is  a  practice  that  should  not  be  tolerated. 

After  the  impurities  are  deposited  in  the  boiler,  they  may  be 
removed  by  the  blow-out  apparatus;  and  if  it  is  possible  to  "lay  off" 
the  boiler  occasionally,  it  should  be  allowed  to  cool  down  slowly,  and 
then  the  water  may  be  drawn  off  and  the  boiler  properly  washed  out. 
A  considerable  amount  of  heat  is  abstracted  from  the  boiler  by  fre- 
quent blowing-off,  and  this  is  a  matter  of  direct  loss,  but  it  is  nothing 
like  so  much  as  would  be  caused  by  the  formation  of  scale. 

Water  may  be  purified  to  a  certain  extent  by  passing  it  through 
a  purifier  before  allowing  it  to  enter  the  boiler.  The  carbonate  and 
sulphate  of  lime  are  precipitated  at  the  same  time  that  the  water  is 
heated.  The  purifier  was  referred  to  under  the  topic  of  "Feed- 
\Yater  Heaters."  The  use  of  soda  for  the  neutralization  of  sulphate 
of  lime  has  already  been  spoken  of;  but  various  compounds  are  on 
the  market  for  overcoming  the  evil  effects  of  other  solids;  and  it  is 
possible,  by  an  analysis  of  the  feed  water,  to  prescribe  a  boiler  com- 
pound that  will  give  satisfactory  results.  Cheap  compounds,  sold 
without  reference  to  the  analysis  of  the  feed -water,  should  be  avoided. 
Caustic  soda  may  be  used  instead  of  the  carbonate,  but  should  be  used 
in  small  quantities.  A  rapid  circulation  of  the  water  will  prevent  the 


88  BOILER  ACCESSORIES 

formation  of  scale,  the  sediment  being  swept  from  the  tubes  or  shell 
into  the  mud-drum,  whence  it  may  be  blown  off.  This  is  one  of  the 
chief  advantages  claimed  for  water-tube  boilers. 

Zinc  plates  have  frequently  been  used  to  prevent  corrosion  and 
incrustation.  The  brass  fittings  are  likely  to  set  up  a  galvanic  action 
with  the  steel  plates;  but  if  the  zinc  is  put  in,  it  will  be  acted  upon 
instead  of  the  iron,  which  otherwise  might  be  rapidly  wasted.  It  is 
claimed  that  this  galvanic  action  prevents  the  formation  of  scale  by 
liberating  hydrogen  at  the  exposed  surfaces.  The  zinc  neutralizes 
the  free  acids  by  combining  with  them,  and  takes  the  place  of  iron 
in  causing  precipitation  of  copper  salts  when  present. 

Kerosene  oil  is  used  to  a  considerable  extent  to  prevent  the  forma- 
tion of  scale  and  to  assist  in  its  removal.  It  breaks  up  and  loosens 
hard  scale,  and  prevents  its  formation.  About  one  quart  a  day  is 
sufficient  for  each  100  horse-power  of  the  boiler. 

BOILER  EXPLOSIONS 

Safety  is  one  of  the  first  requisites  in  a  steam  boiler,  and  must  be 
assured  not  only  by  proper  design  in  the  beginning,  but  by  subsequent 
care  and  proper  maintenance.  The  evil  effects  of  corrosion  and 
incrustation  have  been  clearly  shown;  and  it  is  apparent  that  a  boiler 
which  has  suffered  materially  from  either  cause  is  not  in  condition  to 
stand  full  steam  pressure.  Since  the  explosion  of  a  boiler,  especially 
in  a  city  or  a  factory,  is  likely  to  prove  fatal  to  many  people  and  to 
cause  the  destruction  of  considerable  property,  not  only  by  the  ex- 
plosion itself  but  also  by  fire,  which  almost  invariably  follows  such  an 
occurrence,  it  is  impossible  to  lay  too  great  emphasis  on  the  necessity 
of  seeing  that  the  boiler  is  in  proper  working  condition. 

All  boilers  must  be  carefully  tested — land  boilers,  by  the  State 
Inspectors;  marine  boilers,  by  the  United  States  Inspectors.  The 
boilers  are  carefully  examined  inside  and  outside,  and  subjected  to  a 
hydraulic  pressure  test  50  per  cent  greater  than  the  designed  pressure 
of  steam;  and  if  there  is  the  slightest  sign  of  pitting  or  corrosion,  the 
boiler-plates  may  be  drilled  and  the  thickness  calipered,  the  hole  being 
refilled  by  a  proper  plug.  If  a  boiler  passes  inspection,  a  subsequent 
explosion  will  probably  be  the  result  of  mismanagement,  although 
inspection  is  not  infallible. 


BOILER  ACCESSORIES  89 

The  owner  of  the  boiler  is  usually  held  liable  in  case  of  explosion; 
but  may  protect  himself  from  financial  loss  by  insurance  against 
accident  in  any  of  the  boiler  insurance  companies.  If  so  insured,  the 
Insurance  Inspector,  as  well  as  the  State  Inspector,  examines  the 
boiler;  and  there  is  consequently  less  likelihood  of  an  explosion,  for 
an  insurance  inspector  will  naturally  be  exceedingly  careful  in  th? 
interests  of  his  company. 

The  damage  done  by  an  explosion  is  due  to  the  energy  stored  in 
the  hot  water,  which  energy  can  be  calculated  by  thermodynamic 
methods.  If  a  boiler  contains  a  large  quantity  of  water  at  high  pres- 
sure, and  that  pressure  is  suddenly  relieved,  as  would  happen  in  case 
of  rupture,  a  considerable  portion  of  this  large  volume  of  water  will 
be  turned  instantly  into  steam,  and  the  resulting  explosion  will  ensue. 

When  a  fracture  starts  in  a  boiler-plate,  the  steam  escaping 
through  the  rent  or  opening  tends  to  diminish  the  pressure  rapidly 
within  the  boiler;  and  this  causes  the  rapid  formation  of  a  large 
amount  of  steam.  It  must  be  remembered  that  the  water  in  the  boiler 
at  high  pressure  is  held  in  the  form  of  water  only  because  of  the  high 
pressure  exerted  on  it.  If  this  pressure  is  relieved,  large  quantities  of 
water  will  evaporate  into  steam  at  once,  without  the  application  of 
further  heat.  This  almost  instantaneous  formation  of  a  large  quantity 
of  steam  prevents  the  boiler  pressure  from  dropping,  and  the  fracture 
naturally  widens.  The  larger  the  body  of  hot  water,  the  greater  the 
disaster.  This  accounts  for  the  relative  safety  of  water-tube  boilers. 
The  division  of  the  water  in  such  a  boiler  into  small  masses  in  different 
sections,  prevents  a  violent  explosion.  Should  a  water  tube  burn 
out,  probably  nothing  more  serious  would  happen  than  the  rapid 
escape  of  a  considerable  quantity  of  steam,  which  might  fill  the  boiler- 
room,  drive  out  the  attendants,  and  ultimately  cause  the  destruction 
of  the  boiler  because  of  the  absence  of  water  together  with  a  hot  fire. 
It  would  be  necessary  for  several  water  tubes  to  burst  at  once  in  order 
that  there  should  be  serious  damage  from  such  an  accident. 

Energy.  The  available  energy  in  one  pound  of  hot  water  at 
150  Ibs.  absolute  pressure  and  358°  R,  is  about  42,800  foot-pounds; 
that  is,  it  is  sufficient  to  move  one  pound  nearly  eight  miles;  and  if  at 
250  Ibs.  pressure,  it  has  sufficient  -  energy  to  move  it  nearly  twelve 
miles.  This  energy  may  be  determined  somewhat  as  follows:  From 
the  table  of  the  properties  of  saturated  steam,  given  in  the  back  of  the 


90  BOILER  ACCESSORIES 

book,  it  is  seen  that  at  150  Ibs.  absolute  pressure  (approximately  135 
gauge),  the  temperature  is  358.26°  F.  The  heat  contained  in  a  pound 
of  hot  water  at  this  temperature  will  be  330  B.  T.  IL,  equivalent  to 
330  X  778  =  256,740  foot-pounds.  This  represents  the  total  heat 
energy  in  one  pound  of  hot  water  at  boiler  pressure;  but  since  one 
pound  of  steam  at  atmospheric  pressure  contains  very  many  more 
heat  units  than  a  pound  of  water  at  150  Ibs,  -pressure,  it  is  apparent 
that  only  a  portion  of  this  water  can  evaporate  into  steam,  the  balance 
remaining  as  hot  water.  About  17  per  cent  of  the  total  energy  will  be 
thus  available  in  vaporizing  the  water  into  steam;  or,  approximately, 
42,800  foot-pounds  per  pound  of  water  will  be  developed.  The 
remaining  heat  is  in  the  form  of  hot  water. 

A  cylindrical  boiler  5  feet  in  diameter  and  16  feet  long  is  likely  to 
contain  about  6,600  pounds  of  water  and  22  pounds  of  steam.  Neg- 
lecting the  energy  of  the  steam,  which  is  relatively  small,  the  energy 
in  the  water  due  to  its  expansion  from  water  at  boiler  pressure  into 
steam  at  atmospheric  pressure,  will  be  approximately  6,600  X  42,800 
=  282,480,000  foot-pounds,  or  141,240  foot-tons. 

A  marine  boiler  13  feet  in  diameter  and  12  feet  long  ,would  develop 
approximately  twice  this  energy,  which  would  be  about  equivalent 
to  the  energy  developed  by  the  explosion  of  a  ton  of  gunpowder.  The 
explosion  of  one  boiler  on  a  modern  battleship  would  develop  sufficient 
power  to  lift  the  ship  completely  out  of  the  water.  Of  course  it  must 
be  realized  that  a  large  part  of  this  energy  is  lost,  and  considerable  is 
consumed  in  the  destruction  of  the  boiler  itself,  which  leaves  but  a 
comparatively  small  amount  to  be  expended  in  wrecking  the  im- 
mediate surroundings;  but  it  nevertheless  is  a  fact  that  the  energy 
developed  in  the  explosion  of  a  large  boiler  is  almost  beyond  the  power 
of  comprehension. 

Causes  of  Explosions.  Boiler  explosions  are  usually  the 
result  of  low  water,  grease,  or  scale.  The  two  latter,  by  preventing 
the  transmission  of  heat  from  the  water,  are  likely  to  cause  undue 
overheating  of  the  furnaces  or  tubes,  which  may  result  in  their  collapse; 
these  two  causes — grease  and  scale — have  been  discussed  under  the 
subject  of  " Incrustation." 

Low  water  may  be  caused  by  failure  of  the  water  glass  to  indicate 
properly  the  amount  of  water  in  the  boiler,  or  by  failure  of  the  feed 
pump  to  work  properly. 


BOILER  ACCESSORIES  91 

Safety-valves  have  been  known  to  be  rusted  to  their  seats  so 
tightly  that  they  failed  to  work  at  the  proper  time. 

It  is  seldom  that  a  boiler  can  fail  as  the  result  of  defective  design, 
for  the  laws  in  regard  to  construction,  especially  of  marine  boilers,  are 
very  definite.  Defective  workmanship  or  material,  however,  cannot 
be  easily  discovered;  and  it  is  possible  that  corrosion  or  incrustation 
may  take  place  locally,  without  being  readily  detected;  and,  indeed, 
boiler-plates  may  even  be  tapped,  and  their  thickness  calipered^ 
without  discovering  small  local  weaknesses  which  later  may  cause 
disaster.  Minute  fractures  which  escaped  the  Inspector's  detec- 
tion have  later  become  serious.  The  majority  of  explosions  can 
undoubtedly  be  traced  to  mismanagement  in  either  care  or  operation. 

Defective  Design.  If  a  boiler  is  improperly  set;  if  the  stays  are 
too  small,  too  few,  or  cut  or  bent  to  clear  floats,  pipes,  etc.,  danger  is 
likely  to  result  therefrom.  All  manholes,  targe  handholes,  or  domes 
should  be  strengthened  with  a  reinforcing  plate  to  make  up  for  the 
material  cut  out.  If  the  boiler  is  set  too  rigidly  on  its  seating,  without 
proper  provision  for  its  expansion,  trouble  is  likely  to  follow.  A 
defective  water  circulation  is  likely  to  cause  excessive  incrustation  and 
unequal  expansion  of  the  plating,  which  is  liable  to  open  seams  and 
produce  fractures  in  the  plates. 

Deterioration.  The  strength  of  a  boiler  is  likely  to  be  impaired 
by  fractures,  general  corrosion,  pitting,  or  grooving.  But  external 
corrosion  is  the  cause  of  many  disasters.  It  proceeds  unnoticed  iix 
many  -eases,  and  rupture  may  occur  when  least  expected.  In  the  dis- 
cussion of  "Corrosion,"  it  was  shown  that  improper  setting  of  the 
boiler  would  cause  or  at  least  aggravate  external  corrosion;  and  that, 
on  account  of  the  close  setting  of  the  boiler,  it  was  not  easy  to  get  at 
the  plates  to  examine  them.  The  strength  of  a  boiler  originally  suf- 
ficient to  sustain  high  pressure  may  become  suddenly  reduced  by  over- 
heating or  over-straining,  either  of  which  weakens  the  plates.  Over- 
heating may  be  caused  by  poor  circulation,  lack  of  water,  or  the  accum- 
ulation of  sediment  or  scale.  Over-straining  is  caused  by  sudden 
cooling  and  contraction,  or  equally  by  sudden  expansion.  In  starting 
the  fire  in  a  Scotch  boiler — or,  in  fact,  in  any  boiler  with  a  large  quan- 
tity of  water — care  must  be  taken  that  the  fire  is  started  slowly,  or  the 
boiler,  becoming  overheated  locally,  will  develop  excessive  strains. 


92  BOILER  ACCESSORIES 

Dejects  of  Workmanship.  Defective  workmanship  is  not  of  so 
frequent  occurrence  under  present  conditions  as  formerly,  when  many 
defects  used  to  be  produced  by  careless  punching  of  plates;  but  for 
most  boilers,  and  for  all  marine  boilers  at  present,  punching  is  pro- 
hibited; the  holes  must  be  drilled,  and  the  plate  edges  planed  and 
carefully  calked.  A  rigid  inspection  of  material  is  required,  and  there 
seems  little  danger  of  unsatisfactory  work.  Cheap  boilers  may  of 
course  be  subject  to  various  defects,  but  a  good  boiler  should  be  free 
from  such  troubles.  Material  may  be  defective  and  may  not  be 
readily  detected;  but  the  careful  tests  now  required,  especially  in 
marine  work,  reduce  these  possibilities  to  a  minimum. 

Mismanagement.  The  pressure  in  a  steam  boiler  may  rise 
above  that  at  which  the  safety-valve  has  been  set  to  operate,  because  of 
corrosion  or  overloading  of  the  valve.  Stop-valves  are  sometimes 
placed  between  the  boiler  and  the  safety-valve;  but  this  practice 
should  be  condemned,  as  it  is  possible  that  the  stop-valve  may  be 
closed  when  the  fireman  thinks  the  safety-valve  is  open  to  the  boiler 
pressure.  If  the  size  or  lift  of  the  safety-valve  is  too  small,  steam  may 
be  generated  faster  than  it  can  escape,  in  which  case  the  pressure  will 
rise  in  spite  of  the  safety-valve.  It  has  been  claimed  that  the  blowing- 
off  of  the  safety-valve  when  the  boiler  is  under  excessive  pressure  may 
be  the  cause  of  starting  an  explosion;  but  the  reason  why  this  should 
be  so  does  not  seem  to  be  especially  clear,  and  it  seems  to  be  improb- 
able if  the  opening  of  the  safety-valve  is  sufficient  to  cause  a  reduction 
in  pressure.  Safety-valves  have  sometimes  been  loaded  down  tem- 
porarily to  prevent  leakage  at  working  pressure;  but  such  a  practice 
is  little  short  of  criminal.  If  a  safety-valve  leaks,  it  should  be  re- 
ground,  but  under  no  circumstances  should  the  weight  on  the  lever  be 
altered. 

It  is  a  common  idea  that  when  the  furnace  plates  become  very 
hot,  perhaps  heated  to  redness,  due  to  a  lack  of  water,  and  the  feed  is 
turned  on,  a  violent  explosion  is  sure  to  follow.  Experiments  show 
that  when  a  piece  of  wrought  iron  is  heated  to  redness  and  plunged 
into  a  weight  of  water  three  or  four  times  greater  than  that  of  the  iron, 
a  comparatively  small  quantity  of  steam  is  disengaged.  There  is  no 
reason  to  believe  that  this  quantity  would  be  greater  if  the  iron  were 
in  the  form  of  a  boiler  than  in  the  form  of  a  plate.  If  a  small  quantity 
of  water  were  admitted  to  hot  plates,  the  danger  would 


BOILER  ACCESSORIES  93 

be  greater;  and  while  a  boiler  under  this  condition  might  explode, 
the  comparatively  small  quantity  of  water  in  it  would  make  the  re- 
sulting danger  much  less  than  if  the  boiler  were  under  working  con- 
ditions. 

The  following  experiments  illustrate  the  action  of  cold  water  on 
hot  plates.  A  boiler  25  feet  long  and  6  feet  in  diameter  was  heated 
red  hot  and  the  feed  turned  on.  No  explosion  occurred ;  but  the  sud- 
den contraction  of  the  overheated  plates  caused  the  water  to  pour  out 
in  streams  at  every  seam  and  rivet-hole  as  far  as  the  fire-mark  extended. 
In  another  instance,  the  water  was  almost  entirely  drawn  off  while  the 
fires  were  burning  briskly.  When  the  remaining  water  had  been  con- 
verted into  steam  and  all  the  fusible  plugs  melted  out,  water  at  the  rate 
of  28  gallons  per  minute  in  a  series  of  fine  jets  was  played  on  the  hot 
plates.  Such  treatment  may  ruin  a  boiler  for  further  service,  though 
the  boiler  may  not  explode. 

That  a  tough  paper  or  cloth  is  easily  torn  when  once  a  tear  is 
started,  is  a  well-known  fact.  Similarly  a  boiler-plate  may  be  rup- 
tured at  slight  pressure  if  a  fracture  has  been  started. 

The  position  of  the  fracture  or  hole  has  a  great  influence  on  the 
results.  In  case  a  large  rent  occurs  at  the  top  of  a  cylindrical  boiler, 
the  steam  and  hot  water  may  blow  out  of  the  hole ;  and  the  boiler,  if 
strongly  enough  seated  to  stand  the  reaction,  will  remain  on  its  seat. 
The  damage  to  the  boiler  would  be  slight.  But  suppose  the  same  rent 
were  situated  on  the  under  side  of  the  boiler  near  the  ground  or  floor; 
the  effect  would  be  very  different,  the  reaction  of  the  escaping  steam 
would  probably  blow  the  whole  boiler  through  the  roof. 

Investigation.  When  an  explosion  occurs,  it  should  be  investi- 
gated, not  only  to  fix  the  responsibility  where  it  belongs,  but  also  to 
provide  for  and  take  means  to  prevent  future  disasters.  It  has  been 
customary  to  attribute  all  explosions  to  low  water,  since  it  is  an  easy 
way  to  throw  the  responsibility  from  the  makers  or  owners  upon  the 
fireman,  who,  even  if  living,  cannot  defend  himself.  In  the  investi- 
gation of  an  explosion,  the  weights,  shapes,  positions,  and  directions 
of  the  scattered  pieces  should  be  noted,  so  that  their  original  places 
may  be  known.  The  original  size  and  shape  of  the  boiler  and  of  the 
fittings  should  be  known  as  accurately  as  possible.  The  primary  rent 
may  be  discovered  from  comparison  and  from  deductions  of  the 
directions  taken  by  the  heavier  pieces.  Light  pieces  will  generally 


94  BOILER  ACCESSORIES 

take  the  direction  of  the  escaping  steam,  while  the  heavy  parts  take  an 
opposite  direction,  that  of  the  reaction.  A  careful  examination  of  the 
pieces,  noting  the  age  of  fractures,  thickness  of  plates,  amount  of 
corrosion,  condition  of  plates,  etc.,  will  generally  show  the  cause.  A 
test  of  the  plates  will  in  many  cases  show  any  softening  or  yielding  to 
the  pressure  and  excessive  thinness  caused  by  bulging. 

Prevention.  The  means  taken  to  prevent  boiler  explosions 
from  most  of  the  above-mentioned  causes,  have  already  been  given. 
It  is  of  primary  importance  that  at  the  start  only  a  well-designed  and 
well-made  boiler  should  be  used.  The  matter  of  type  is  not  of  so 
much  importance;  but  it  is  well  to  use  a  sectional  boiler  in  large  cities 
or  in  buildings  where  many  people  are  employed.  There  are  many 
methods,  some  of  which  have  been  discussed,  that  are  taken  to  pre- 
vent deterioration  by  corrosion,  fracture,  etc.  Proper  setting  is  of 
great  importance  in  this  matter.  Mishaps  from  mismanagement 
may  be  greatly  lessened  by  the  employment  of  licensed  attendants. . 
A  boiler  should  never  be  in  the  hands  of  a  man  who  is  not  thoroughly 
competent  to  run  it.  The  most  effective  method  to  prevent  explosions 
is  the  law  of  the  State,  compelling  regular,  thorough  inspection  and 
licensed  firemen.  The  inspection  by  the  Boiler  Insurance  companies 
is  also  an  efficient  method. 

During  a  period  of  eleven  and  one-half  years,  70,000  boilers  were 
inspected  by  Boiler  Insurance  companies.  It  was  estimated  that  there 
were  140,000  in  use  during  that  time.  Of  the  inspected  boilers,  there 
were  23  explosions  and  50  collapses,  resulting  in  27  deaths  from  ex- 
plosions, and  28  deaths  from  collapses.  The  explosion  rate  was  1  in 
11,000;  and  the  death  rate,  1  in  14,600.  The  uninsured  boilers  did 
not  make  so  good  a  showing,  the  death  rate  being  1  in  5,000  boilers, 
or  about  3  times  as  high  as  among  the  insured  boilers, 

FUEL 

There  are  various  kinds  of  fuel  used  in  steam  production,  loca- 
tion, cost,  and  the  exigencies  of  the  case  being  the  deciding  factors. 
Usually  the  kind  of  fuel  is  determined  upon,  and  the  boiler  designed 
with  that  end  in  view.  Sometimes,  however,  the  fuel  must  be  adapted 
to  the  boiler. 

Coal.  Coal  is  not  only  the  most  important  fuel,  but  in  many 
localities  the  only  one  available.  It  is  of  vegetable  origin,  being  the 


BOILER  ACCESSORIES 


95 


long-decayed  product  of  ancient  forests.  Frequently  it  occurs  so 
mixed  with  earthy  matter  as  to  be  of  little  value;  but  the  supply  of 
good  coal  is  still  abundant,  and  likely  to  be  so  for  some  time  to  come. 

The  most  important  elements  in  coal  are  hydrogen,  producing 
62,000  B.  T.  U.  per  pound,  and  carbon,  producing  14,500  B.  T.  U. 
per  pound.  Although  several  coals  may  have  the  same  total  per- 
centage of  combustible  material  and  ash,  the  heat  values  may  not  be 
the  same,  because  heat  value  depends  upon  the  amounts  of  hydrogen 
and  carbon  they  contain.  The  heat  value  of  fuels  is  determined  by 
chemical  analysis,  or  by  calorimetric  test,  and  varies  for  coal  from 
different  localities.  The  following  table  is  compiled  from  several 
sources : 

ANALYSIS  AND  HEAT  VALUE  OF  VARIOUS  COALS 


POUNDS  OF 

KIND  OF  COAL 

PER  CENT 
OP  ASH 

THEORETICAL 
B.  T.  U. 

WATER 
EVAPORATED 
PER  POUND 

PER  POUND 

(THEORETI- 

CAL) 

Penn.  Anthracite 

3.49 

14,199 

14.70 

Penn.  Anthracite 

2.90 

14,221 

14.72 

Peun.  Cannel 

15.02 

13,143 

13.60 

Penu.  Connellsville 

6.50 

13,368 

13.84 

Penn.  Semi-bituminous 

10.70 

13,155 

13.62 

Penn.  Brown 

9.50 

12,324 

12.75 

Kentucky  Caking 
Kentucky  Canuel 
Kentucky  Lignite 

2.75 
2.00 
7.00 

14,391 
15,198 
9,326 

14.89 
16.76 
9.65 

Indiana  Caking 

5.66 

14,146 

14.64 

Indiana  Cannel 

6.00 

13,097 

13.56 

Maryland  Cumberland 

13.88 

12,226 

12.65 

Arkansas  Lignite 

5.00 

9,215 

9.54 

Colorado  Lignite 

9.25 

13,562 

14.04 

Texas  Lignite 

,  4.50 

12,962 

13.41 

Washington  Lignite 

3.40 

11,551 

11.96 

In  practice,  no  fuel  gives  its  theoretical  evaporation  value.  On 
account  of  several  losses  that  are  inevitably  incurred,  heat  is  radiated 
from,  and  conducted  away  by,  the  boiler  setting.  The  admission  of 
too  much  air  into  the  furnace,  either  through  the  doors  or  through 
cracks  in  the  setting,  reduces  the  theoretical  evaporation  value.  Im- 
proper firing  causes  considerable  loss;  and  errors  in  design,  con- 
struction, or  setting  reduce  the  efficiency. 

The  different  kinds  of  coal  are  too  numerous  to  be  easily  named, 
but  in  general  they  may  be  classified  as  anthracite  or  bituminous,  com- 


96  BOILER  ACCESSORIES 

monly  called  hard  or  soft  respectively,  of  which  there  are  various  sub- 
divisions. 

Anthracite.  Anthracite  coal  consists  almost  entirely  of  carbon, 
but  has  a  small  amount  of  hydrocarbon.  Good  anthracite  is  lustrous, 
hard,  flinty,  but  breaks  up  easily  under  high  temperature.  It  burns 
with  very  little  flame  and  smoke,  and  gives  an  intense  heat.  It  does 
not  ignite  so  readily  as  the  softer  varieties  of  coal;  but  once  started, 
the  fire  requires  less  attention.  It  is  an  excellent  fuel  where  the  pro- 
duction of  smoke  is  a  decided  objection. 

Semi=Anthracite.  This  is  a  coal  between  pure  anthracite  and 
semi-bituminous.  It  is  not  so  hard  as  anthracite,  and  burns  more 
freely.  It  is  not  so  compact  as  anthracite,  and  burns  with  a  short 
flame,  the  anthracite  having  practically  no  flame. 

Semi=Bituminous.  This  is  the  next  softer  grade  of  coal.  It 
burns  more  freely  than  either  anthracite  or  semi-anthracite,  contains 
more  volatile  hydrocarbon,  and  is  a  valuable  coal  for  steaming  pur- 
poses. 

Bituminous.  Bituminous  coal  forms  by  far  the  larger  portion  of 
steam  coal.  It  contains  a  large  but  varying  amount  of  hyrocarbon  or 
bituminous  matter.  Unless  fired  with  care,  it  will  produce  a  consider- 
able amount  of  smoke  and  clinkers. 

Dry  Bituminous.  This  is  a  black  coal  with  a  resinous  luster. 
It  burns  freely,  and  kindles  with  much  less  difficulty  than  the  anthra- 
cites. It  is  hard,  but  is  easily  splintered.  When  burning,  it  gives  a 
moderate  amount  of  flame,  with  but  little  smoke,  and  does  not  cake. 
It  is  found  chiefly  in  Maryland  and  Virginia. 

Caking  Bituminous.  This  contains  less  carbon  and  more  hydro- 
carbon than  the  former  class.  It  is  not  so  black;  is  more  resinous; 
and,  under  intense  heat,  readily  forms  into  a  solid,  pasty  mass.  Un- 
less frequently  broken  up,  this  pasty  mass  forms  a  blanket  over  the 
grate,  and  checks  the  draft.  Caking  bituminous  is  a  valuable  coal 
for  the  manufacture  of  gas.  It  is  mined  chiefly  in  the  Mississippi 
valley. 

Cannel.  Cannel  or  long-flame  bituminous  coal  produces  a  con- 
siderable quantity  of  smoke.  It  is  mined  chiefly  in  Pennsylvania, 
Indiana,  and  Missouri;  and  is  a  free-burning  coal,  with  a  strong 
tendency  to  cake.  It  is  largely  used  for  open-grate  purposes. 

Lignite.    Lignite,  or  brown  coal  is  intermediate  between  coal  and 


BOILER  ACCESSORIES  97 

peat.  It  is  made  up  mostly  of  carbon,  with  some  moisture  and 
mineral  matter.  Poor  varieties  are  of  little  value.  Good  lignite 
kindles  with  ease,  and  burns  freely,  but  is  likely  to  contain  a  con-- 
siderable  amount  of  water,  and  unless  kept  in  a  dry  place  will  absorb 
moisture.  It  is  not  a  -very  good  fuel,  but  is  used  in  some  localities 
where  other  varieties  are  more  expensive.  It  comes  largely  from 
Colorado,  Texas,  and  Washington. 

Peat.  This  is  a  form  of  fuel  consisting  of  decayed  roots,  tree- 
trunks,  etc.,  and  earthy  matter.  It  is  found  in  swamps  and  bogs,  and 
has  been  in  process  of  decomposition  a  much  shorter  time  than  any 
of  the  coals.  It  is  cut  out  in  blocks  and  dried.  Peat  has  a  specific 
gravity  of  .4  to  .5,  but  it  can  be  compressed  to  a  much  greater  density. 
It  is  necessary  that  peat  should  be  kept  in  a  dry  place,  for  it  will  readily 
absorb  moisture. 

Coke.  This  is  made  by  driving  off  by  heat  the  hydrocarbon  of 
bituminous  or  semi-bituminous  coals.  It  may  be  made  in  gas  retorts, 
as  a  by-product  of  gas  production ;  or  it  may  be  made  in  coking  ovens, 
the  gas  being  the  by-product.  The  latter  form  of  coke  is  more  valu- 
able as  a  fuel.  If  the  coal  is  very  moist,  or  if  steam  is  used  in  the  coking 
process,  as  in  the  manufacture  of  water  gas,  the  sulphur  is  burned  out. 
Coke  burns  without  flame;  and,  with  a  free  supply  of  air,  will  make 
an  intensely  hot  fire. 

Charcoal.  Charcoal  is  practically  never  used  for  steam  fuel,  its 
chief  use  being  for  household  or  manufacturing  purposes.  It  is  made 
by  evaporating  the  volatile  matter  from  wood,  either  by  partial  com- 
bustion or  by  heating  in  retorts.  About  50  bushels  of  charcoal  can  be 
obtained  from  a  cord  of  wood. 

Culm.  This  is  a  name  given  to  refuse  dust  at  the  coal  mines, 
sometimes  called  slack.  It  can  be  bought  at  the  mines  at  a  very  low 
rate;  but  the  cost  of  transportation  prohibits  its  use  except  in  the 
immediate  vicinity  of  the  mines.  On  account  of  its  fineness,  it  cannot 
be  burned  in  an  ordinary  grate,  and  is  usually  blown  into  the  boiler 
with  a  sufficient  quantity  of  air,  where  it  burns  somewhat  like  a  gas. 
A  grate  beneath  usually  contains  a  moderate  fire,  which  keeps  the 
culm  well  ignited  and  prevents  the  loss  of  any  particles  that  might 
otherwise  drop  out  of  the  furnace. 

Wood.  There  are  two  principal  divisions  of  wood — hardwood, 
which  is  compact  and  comparatively  heavy,  such  as  oak,  ash,  and 


98  BOILER  ACCESSORIES 

hickory;  and  soft  wood,  which  is  of  soft  and  porous  texture  and  of  less 
specific  gravity,  such  as  pine,  birch,  and  poplar.  Wood  contains 
,  considerable  moisture,  even  if  left  to  season  in  a  dry  place;  and  after 
being  thoroughly  dried,  it  will  absorb  and  retain  from  10  to  20  per  cent 
of  moisture.  Kiln-dried  wood  contains  nearly  8,000  B.  T.  U.  per 
pound,  while  the  average  wood,  containing  about  25  per  cent  of 
moisture,  has  a  heating  value  of  about  6,000  B.  T.  U. 

The  chemical  composition  of  different  woods  is  nearly  the  same, 
and  pound  for  pound  one  class  of  wood  contains  about  the  same 
heating  value  as  another.  Pine  weighs  about  half  as  much  as  oak 
per  cubic  foot,  and  a  cord  of  such  wood  contains  about  half  the  heating 
value  that  a  cord  of  oak  would  contain. 

Sawdust  and  shavings  are  frequently  used  as  fuel  in  sawmills 
and  planing  mills.  This  kind  of  fuel  is  blown  into  the  furnace  with 
air  from  a  fan,  and  makes  an  intense  heat.  A  fine  grate  at  the  bottom 
collects  the  burning  embers,  which  might  otherwise  drop  into  the  ash- 
pan.  In  mills  where  sawdust  and  shavings  are  used,  they  are  a  by- 
product. 

Straw.  Threshing  machines  through  the  West  use  straw  almost 
entirely  for  fuel.  It  gives  an  intense  heat,  furnishing  5,000  to  6,000 
heat  units  per  pound ;  and  this  is  a  quick  and  easy  way  to  get  rid  of  it. 

Bagasse  is  the  fibrous  portion  of  the  sugar-cane  left  after  the  juice 
has  been  extracted.  In  the  modern  process  of  sugar  manufacture, 
the  cane  is  pressed  so  tightly  that  it  is  ready  for  fuel  without  further 
treating.  Under  favorable  conditions  it  forms  an  excellent  fuel.  The 
pressed  cane  is  a  by-product  which  must  in  some  way  be  got  rid  of. 
It  is  usually  fed  into  the  furnace  through  an  automatic  hopper;  or  it 
may  be  dumped  in  the  fire-room  and  fed  into  the  furnace  by  hand. 
The  furnace  is  constructed  of  brick,  independent  of  the  boilers;  and 
when  bagasse  is  consumed  at  a  high  temperature,  the  oxygen  contained 
in  it  is  nearly  sufficient  to  satisfy  the  carbon  and  hydrogen,  so  that 
little  air  from  the  outside  is  required.  Such  material,  of  course, 
cannot  be  fed  into  an  ordinary  furnace. 

Liquid  Fuels.  These  consist  of  petroleum  and  its  products,  and 
their  use  has  become  quite  extensive  in  the  last  few  years.  The  field 
would  undoubtedly  be  wider  were  there  less  difficulty  in  obtaining  a 
regular  and  constant  supply.  The  greatest  quantities  of  petroleum 
oil  are  produced  in  the  United  States  and  Russia.  Large  quantities 


BOILER  ACCESSORIES 


99 


are  found  on  the  Pacific  Coast,  especially  in  Southern  California;  and 
in  that  section  of  the  country,  oil  is  used  as  fuel  to  a  greater  extent 
than  in  the  East,  being  largely  used  on  tugboats,  ferryboats,  and  loco- 
motives. 

The  following,  approximately,  is  the  composition  of  petroleum: 
Carbon  82  to  87  per  cent. 

Hydrogen  1 1  to  15  per  cent. 

Oxygen     .  r5¥  to  6  per  cent. 

The  theoretical  heating  power  of  petroleum  is  approximately 
20,000  B.  T.  U.  per  pound/which  is  nearly  half  as.  much  again  as 
that  of  good  coal.  Oil  has  a  further  advantage  over  coal,  in  that  no 
unburned  fuel  necessarily  passes  through  the  furnace,  and  there  is  no 
ash — an  important  item  in  marine  work. 

The  composition  and  specific  gravity  of  petroleums  vary  con- 
siderably, many  of  the  lower  grades  being  unsafe  on  account  of  their 
low  flash-point. 

The  fuel  is  fed  into  the  furnace  through  an  atomizer  operated 
either  by  steam  or  by  compressed  air.  Several  types  of  such  de- 
vices are  shown 
in  Fig.  72.  The 
use  of  the  oil  as  a 
fuel  can  be  readily 
controlled  by  the 
simple  manipula- 
tion of  a  valve;  and 
if  the  fire  is  once 
regulated  to  pro- 
duce the  required 
heat,  it  can  be  kept 
at  that  point  with 
very  little  care. 
The  fire  can  be 
started  with  slight 
trouble,  and  can  be  extinguished  instantly.  The  vaporizing  efficiency 
of  oil  is  much  greater  than  that  of  coal;  and  on  the  Pacific  Coast, 
where  oil  can  be  readily  obtained,  it  is  a  much  more  economical  fuel. 
If  burned  properly,  without  too  heavy  an  air-blast,  there  should  be  no 
production  of  smoke.  A  considerable  saving  may  be  effected  in  the 


C.Cha.mber  Burner 
Fig.  72.    Types  of  Atomizers  for  Liquid  Fuel. 


100  BOILER  ACCESSORIES 

fire-room  force,  one  man  being  able  to  operate  several  burners.  There 
is,  of  course,  danger  from  explosion,  on  account  of  vapor  which 
rises  from  the  fuel;  but  if  the  fuel  tank  is  thoroughly  ventilated,  there 
is  little  danger  from  this  source. 

Oil  fuel  may  be  used  to  advantage  in  what  is  called  mixed  firing ; 
that  is,  the  oil  may  be  sprayed  onto  the  bed  of  burning  coal.  This 
has  been  condemned  by  many  engineers,  but  it  has  nevertheless  gained 
considerable  headway,  and,  under  proper  conditions,  has  given  satis- 
factory results.  It  is  beyond  the  scope  of  this  work  to  go  minutely 
into  the  subject  of  oil  fuel;  but  for  further  information  the  student  is 
referred  to  the  reports  of  the  Oil  Fuel  Boards  of  the  U.  S.  Navy  and  of 
the  British  Admiralty. 

Gas.  Gas  has  many  advantages  over  any  other  kind  of  fuel. 
There  are  four  different  varieties — natural  gas,  coal  gas,  water  gas, 
and  producer  gas.  Natural  gas  is  used  largely  in  the  vicinity  of  Pitts- 
burg,  Buffalo,  and  some  parts  of  Indiana,  both  for  illuminating  and 
for  steam  purposes.  Where  natural  gas  is  plentiful,  it  is  by  far  the 
cheapest  fuel  that  can  be  used. 

Coal  gas,  made  by  the  distillation  of  coal,  and  water  gas,  obtained 
by  the  decomposition  of  steam  by  incandescent  carbon,  have  been 
used  both  for  lighting  and  for  fuel ;  but  in  most  cases  these  gases  may 
be  used  to  greater  economy  directly  in  the  cylinder  of  a  gas  engine 
than  as  fuel  under  a  steam  boiler.  The  same  may  be  said  of  pro- 
ducer gas,  which  is  made  by  blowing  steam  and  air  through  incandes- 
cent coal. 

The  relative  values  of  these  gases  for  evaporation,  are  shown  in 
the  following  table: 

EVAPORATIVE  POWER  OF  GASES 

NATURAL  GAS  COAL  GAS  WATER  GAS  PRODUCER  GAS 
Cubic  feet  of  gas                   1,000              1,000             1,000  1,000 

Pounds  of  water  evap- 
orated 893  591  262  115 

Experiments  in  Pittsburg  have  shown  that  1,000  cubic  feet  of 
natural  gas  equals  80  to  133  pounds  of  coal.  The  coal  used  in  the  com- 
parison varied  from  12,000  to  13,000  B.  T.  U.  per  pound. 

The  Western  Society  of  Engineers  has  stated  that  one  pound  of 
good  coal  is  equivalent  in  heating  value  to  1\  cu.  ft.  of  natural  gas. 


BOILER  ACCESSORIES  101 

As  in  the  case  x>f  petroleum,  the  economy  of  burning  gaseous  fuels 
depends  upon  the  locality. 

Artificial  Fuels.  The  waste  of  charcoal,  coal,  sawdust,  etc.,  is 
often  pressed  into  cakes  or  briquettes,  by  means  of  some  adhesive 
mixture,  with  compression.  Wood  tar,  coal  tar,  and  clay  are  used,  ac- 
cording to  convenience.  These  cakes  are  compact,  can  be  stored  in 
small  space,  and  are  used  where  good  fuels  are  difficult  to  obtain. 

STEAM  BOILER  TRIALS 

The  object  of  a  boiler  trial  is  to  determine  the  quantity  and 
quality  of  steam  that  the  boiler  will  supply  under  given  conditions, 
the  horse-power  of  the  boiler,  the  amount  of  fuel  it  takes  to  make  the 
required  steam,  and  its  efficiency. 

The  quantity  of  steam  is  taken  as  the  amount  of  water  evaporated, 
which j  of  course,  is  the  total  amount  fed  into  the  boiler  during  the  test 
the  water-level  being  the  same  at  the  beginning  and  the  end. 

The  quality  of  the  steam  can  be  determined  by  some  form  of 
calorimeter  already  described;  and  the  efficiency  is  the  ratio  of  the 
heat  units  utilized  in  evaporating  the  water  to  the  total  heat  supplied  to 
the  boiler.  The  heat  utilized  in  evaporation  can  be  found  by  multi- 
plying the  number  of  pounds  of  feed-water  by  the  number  of  heat 
units  required  to  change  the  water  at  the  temperature  of  the  feed  into 
steam  at  gauge  pressure.  The  heat  units  supplied  can  be  determined 
by  carefully  weighing  the  fuel  used  during  the  test,  and  deducting  the 
amount  of  ash  and  unburned  fuel  going  through  the  grates,  with 
proper  allowance  for  moisture,  multiplying  the  result  by  the  total  heat 
of  combustion  of  the  fuel.  The  heat  of  combustion  can  be  obtained 
by  calculation,  or  by  means  of  a  fuel  calorimeter. 

Under  a  short  test  the  boiler  must  be  in  good  working  order  and 
fired  for  some  hours  before  the  beginning  of  the  test,  so  that  the  brick- 
work and  chimney  may  be  thoroughly  heated.  Shortly  before  the 
test  is  begun,  the  fire  may  be  allowed  to  burn  low;  and  by  reducing 
the  amount  of  steam  taken  from  the  boiler,  the  pressure  can  be  kept 
constant.  The  fire  may  then  be  drawn,  the  grate  cleaned,  and  a  new 
fire  quickly  started,  with  wood  and  fresh  coal.  Toward  the  end  of  the 
test  the  fire  may  be  allowed  to  burn  low,  and  at  the  close  may  be  drawn 
and  quenched  with  water,  the  unburned  fuel  being  allowed  for.  In 
a  long  test  of  twenty-four  hours  or  more,  this  is  not  necessary. 


102  BOILER  ACCESSORIES 

If  the  boiler  is  fed  by  a  steam  pump,  the  pump  should  be  run  b) 
steam  taken  from  some  other  boiler,  if  convenient;  if  not,  the  amount 
of  steam  used  by  the  pump  must  be  determined  and  allowed  for.  If 
the  feed-water  is  supplied  by  an  injector,  it  will  take  steam  .from  the 
boiler  itself.  About  2  per  cent  of  this  steam  is  consumed  in  forcing  the 
water  into  the  boiler,  the  remainder  going  to  heat  the  feed-water. 

During  the  boiler  trial,  observations  of  temperatures  and  pres- 
sures should  be  made  at  the  same  time,  and  at  about  15-minute  inter- 
vals. In  order  to  obtain  the  result  of  the  test,  the  following  must  be 
known : 

1.  Amount  (in  pounds)  of  coal  burned,  and  number  of  pounds  of  ashes 
left; 

2.  Number  of  pounds  of  water  pumped  into  boiler; 

3.  Temperature  of  feed- water  when  it  enters  boiler; 

4.  Pressure  of  steam  in  boiler; 

5.  Quality  of  steam  discharged  from  boiler — that  is,  the  per  cent  of 
moisture  in  the  steam. 

The  coal  for  the  furnace  can  be  conveniently  weighed  in  barrels, 
and  may  be  fired  directly  from  these  barrels  or  dumped  on  the  fire- 
room  floor.  The  barrels  should  be  carefully  weighed  when  full  and 
empty,  and  the  time  recorded,  so  that  there  may  be  no  possibility  of 
counting  one  barrel  twice  or  omitting  any.  The  rate  of  combustion 
will  be  fairly  uniform,  and  the  calculations  at  the  times  of  emptying 
the  barrel  will  fairly  indicate  whether  or  not  an  error  has  been  made. 
Any  unburned  coal  should  be  weighed,  and  the  amount  subtracted. 

The  condition  of  the  fire  for  a  twenty-four-hour  test  should  be  the 
same  at  the  beginning  and  the  end.  This  condition  is  estimated  by 
the  eye;  and  unless  great  care  is  used,  an  appreciable  error  is  likely 
to  be  made  If  the  coal  consumption  is  15  to  20  Ibs.  per  square  foot  of 
grate  surface,  an  error  of  two  inches  in  estimating  the  thickness  of  the 
fire  may  cause  an  error  of  as  much  as  2  per  cent  in  the  final  results. 
The  wood  used  in  starting  the  fire  should  be  carefully  weighed, 
and  may  be  considered  as  equal  to  -fa  of  the  same  weight  of  coal. 
The  clinker  and  ashes  should  be  carefully  collected  and  weighed,  and 
a  sample  of  the  ashes  examined  to  obtain  the  amount  of  unburned 
fuel. 

There  are  several  ways  of  determining  the  amount  of  water 
pumped  into  the  boiler.  The  best  method  is  to  weigh  it  in  tanks  or 
barrels  set  upon  standard  scales.  There  should  be  two  or  more 


BOILER  ACCESSORIES  103 

barrels  of  sufficient  size,  so  that  the  filling  and  emptying  may  not  be 
hurried.  They  should  be  set  high  enough  to  discharge  readily  into 
the  tank  or  hot  well  from  which  the  feed-water  is  drawn.  The  valves 
should  be  large  and  should  open  quickly,  so  that  the  emptying  may 
not  be  delayed.  If  barrels  are  used, they  should  be  numbered,  and  the 
weight  of  each  accurately  noted,  so  that  there  may  be  no  mistake  in  de- 
ducting the  weight  of  a  barrel  from  the  total  weight  of  barrel  and  water. 
When  one  barrel  is  being  emptied,  the  other  may  be  filled.  The 
weigher  must  use  care  and  intelligence;  otherwise  he  may  become 
confused  in  his  records,  as  in  a  boiler  of  considerable  size  the  barrels 
fill  and  empty  rapidly.  At  the  beginning  of  the  test,  the  level  of  the 
water  in  the  hot  well  should  be  recorded,  and  at  the  end  of  the  test 
should  be  brought  to  the  same  mark.  If  inconvenient  to  weigh  the 
water,  it  may  be  measured  by  a  meter ;  but  if  a  meter  is  used,  it  should  be 
tested  and  its  error  determined  under  like  conditions  of  temperature 
and  pressure.  The  feed-water  should  be  free  from  air,  as  otherwise 
too  large  a  meter  reading  will  be  recorded. 

The  level  in  the  water-glass  of  the  boiler  should  be  carefully  noted 
at  the  beginning  and  end  of  the  test.  If  possible,  the  level  should  be 
constant  throughout  the  test;  and  if  there  is  any  difference  between 
the  beginning  and  the  end,  due  allowance  should  be  made  for  it. 

The  temperature  of  the  feed -water  can  be  taken  best  by  means  of  a 
thermometer  in  a  cup  filled  with  oil  screwed  into  the  feed-pipe  near  the 
check-valve.  If  the  temperature  is  nearly  constant,  readings  at  15- 
minute  intervals  will  suffice;  otherwise  readings  should  be  taken 
every  five  minutes. 

The  steam  pressure  shown  by  the  gauge  should  be  as  nearly  con- 
stant as  possible  throughout  the  test,  and  should  be  practically  the 
same  both  at  the  beginning  and  at  the  end.  Gauge  readings  should  be 
recorded  every  15  minutes,  and  the  fireman  should  see  that  the  pres- 
sure is  constant.  The  gauge  should  be  tested,  and  corrected  if  neces- 
sary. 

Barometric  readings  should  also  be  taken,  two  or  three  being 
sufficient  for  a  ten-hour  run.  These  readings,  in  inches,  may  be  made 
to  indicate  pounds  pressure  by  multiplying  by  .491,  this  being  the 
weight  of  one  cubic  inch  of  mercury.  If  the  trial  is  on  a  vertical  boiler 
which  furnishes  superheated  steam  because  of  the  heat  being  in  con- 
tact with  the  tubes  above  the  water-level,  both  the  pressure-gauge  and 


104  BOILER  ACCESSORIES 

the  thermometer  should  be  used,  so  that  the  amount  of  superheating 
can  readily  be  found  by  subtracting  the  temperature  due  to  pressure 
(obtained  from  the  steam  tables)  from  the  temperature  readings. 

The  quality  of  steam  can  readily  be  determined  by  a  calorimeter. 
If  there  is  sufficient  steam  space  within  the  boiler,  from  1  to  2  per  cent 
priming  will  generally  result.  If  the  steam  space  is  inadequate,  there 
will  be  more  priming.  If  more  than  2  per  cent  priming  is  present,  the 
steam  will  blow  white  from  the  gauge-cocks  when  opened ;  if  less  than 
2  per  cent,  it  will  appear  blue. 

The  above  observations  are  of  the  more  important  class,  and  must 
be  taken.  In  addition  to  these,  it  is  well  to  take  samples  of  the  flue  gas 
at  intervals  and  from  various  places  in  the  furnace  or  chimney,  the 
object  being  to  determine  whether  there  is  a  sufficient  supply  of  air 
admitted,  or  whether  there  is  too  much.  The  draft  of  the  chimney 
may  be  measured  by  means  of  a  U-tube  partially  rilled  with  water,  or 
by  a  draft-gauge. 

It  is  well  to  bear  in  mind  that  in  making  the  boiler  test  the  utmost 
care  must  be  used,  both  in  taking  observations  and  in  recording  them, 
and  in  working  up  the  results  of  the  trial.  A  committee  of  the  Ameri- 
can Society  of  Mechanical  Engineers  has  recommended  a  code  of 
rules  for  boiler  trials,  and  the  following  standard  form  for  recording 
results.  These  are  too  voluminous  for  complete  reproduction,  and 
they  can  be  found  in  full  in  Vol.  XXI  of  the  Proceedings  of  the  above 
Society  for  the  year  1900.  The  following  code  of  rules  is  practically 
an  abstract  of  the  above-mentioned  code: 

PRELIMINARIES  TO  A  TEST 

1.  In  preparing  for  and  conducting  trials  of  steam  boilers, 
the  specific  object  of  the  proposed  trial  should  be  clearly  defined  and 
steadily  kept  in  view. 

2.  Measure  and  record  the  dimensions,  position,  etc.,  of  grate 
and  heating  surfaces,  flues,  and  chimneys;  proportion  of  air-space  in 
the  grate-surface;  kind  of  draught,  natural  or  forced. 

3.  Put  the  boiler  in  good  condition.     Have  heating  surface 
clean  inside  and  out;  grate-bars  and  sides  of  furnace  free  from  clinkers; 
dust  and  ashes  removed  from  back  connections;  leaks  in  masonry 
stopped;  and  all  obstructions  to  draught  removed.     See  that  the 
damper  will  open  to  full  extent,  and  that  it  may  be  closed  when  desired, 


BOILER  ACCESSORIES  105 


Test  for  leaks  in  masonry  by  firing  a  little  smoky  fuel  and  immediately 
closing  damper.  The  smoke  will  escape  through  the  leaks  if  there  be 
such. 

4.  Have  an  understanding  with  the  parties  in  whose  interest 
the  test  is  to  be  made,  as  to  the  character  of  the  coal  to  be  used.    The 
coal  must  be  dry;  or,  if  wet,  a  sample  must  be  dried  carefully,  and  a 
determination  of  the  amount  of  moisture  in  the  coal  must  be  made, 
the  calculation  of  the  results  of  the  test  being  corrected  accordingly. 
Wherever  possible,  the  test  should  be  made  with  standard  coal  of  a 
known  quality.     For  that  portion  of  the  country  east  of  the  Alleghany 
mountains,  good  anthracite  egg  coal  or  Cumberland  semi-bituminous 
coal  may  be  taken  as  the  standard  for  making  tests.     West  of  the 
Alleghany  mountains  and  east  of  the  Missouri  river,  Pittsburg  lump 
coal  may  be  used. 

In  all  important  tests,  a  sample  of  coal  should  be  selected  for 
chemical  analysis. 

5.  Establish  the  correctness  of  all  apparatus  used  in  the  test 
for  weighing  and  measuring.     These  are:  1.     Scales  for  weighing 
coal,  ashes,  and  water.     2.     Tanks  or  water-meters  for  measuring 
water.     Water-meters,  as  a  rule,  should  only  be  used  as  a  check  on 
other  measurements.     For  accurate  work  the  water  should  be  weighed 
or  measured  in  a  tank.     3.    Thermometers  and  pyrometers  for  taking 
temperatures  of  air,  steam,  feed-water,  waste  gases,  etc.    4.    Pressure- 
gauges,  draft-gauges,  etc. 

6.  Before  beginning  a  test,  the  boiler  and  chimney  should  be 
thoroughly  heated  to  their  usual  working  temperature.     If  the  boiler 
is  new,  it  should  be  in  continuous  use  at  least  a'  week  before  testing,  so 
as  to  dry  the  mortar  thoroughly  and  heat  the  walls. 

7.  Before  beginning  a  test3  the  boiler  and  connections  should 
be  free  from  leaks;  and  all  water  connections,  including  blow  and 
extra  feed-pipes,  should  be  disconnected  or  stopped  with  blank  flanges, 
except  the  particular  pipe  through  which  water  is  to  be  fed  to  the 
boiler  during  the  trial.     In  locations  where  the  reliability  of  the  power 
is  so  important  that  an  extra  feed-pipe  must  be  kept  in  position,  and  in 
general  when,  for  any  other  reason,  water-pipes  other  than  the  feed- 
pipes cannot  be  disconnected,  such  pipes  may  be  drilled  so  as  to  leave 
openings  in  their  lower  sides,  which  should  be  kept  open  throughout 
the  test  as  a  means  of  detecting  leaks  or  accidental  or  unauthorized 


106  BOILER  ACCESSORIES 

opening  of  valves.  During  the  test  the  blow-off  pipe  should  remain 
exposed. 

If  an  injector  is  used  it  must  receive  steam  directly  from  the  boiler 
being  tested,  and  not  from  a  steam-pipe  or  from  any  other  boiler. 

See  that  the  steam  pipe  is  so  arranged  that  water  of  condensation 
cannot  run  back  into  the  boiler.  If  the  steam  pipe  has  such  an  inclina- 
tion that  the  water  of  condensation  from  any  portion  of  the  steam- 
pipe  system  may  run  back  into  the  boiler,  it  must  be  trapped  so  as  to 
prevent  this  water  getting  into  the  boiler  without  being  measured. 

8.  A  test  should  last  at'  least  ten  hours  of  continuous  running, 
and  twenty-four  hours  whenever  practicable. 

9.  The  conditions  of  the  boiler  and  furnace  in  all  respects 
should  be,  as  nearly  as  possible,  the  same  at  the  end  as  at  the  beginning 
of  the  test.    The  steam  pressure  should  be  the  same,  the  water-level 
the  same,  the  fire  upon  the  grates  should  be  the  same  in  quantity  and 
condition,  and  the  walls,  flues,  etc.,  should  be  of  the  same  temperature. 
To  secure  as  near  an  approximation  to  exact  uniformity  as  possible 
in  conditions  of  the  fire  and  in  temperatures  of  the  walls  and  flues, 
the  following  method  of  starting   and    stopping  a   test   should   be 
adopted. 

10.  Standard    Method.     Steam  being  raised   to   the   working 
pressure,  remove  rapidly  all  the  fire  from  the  grate,  close  the  damper, 
clean  the  ash-pit,  and  as  quickly  as  possible  start  a  new  fire  with 
weighed  wood  and  coal,  noting  the  time  of  starting  the  test  and  the 
height  of  the  water-level  while  the  water  is  in  a  quiescent  state,  just 
before  lighting  the  fire. 

At  the  end  of  the  test,  remove  the  whole  fire,  clean  the  grates.and 
ash-pit,  and  note  the  water-level  when  the  water  is  in  a  quiescent 
state ;  record  the  time  of  hauling  the  fire  as  the  end  of  the  test.  The 
water-level  should  be  as  nearly  as  possible  the  same  as  at  the  beginning 
of  the  test.  If  it  is  not  the  same,  a  correction  should  be  made  by  com- 
putation, and  not  by  operating  pump  after  test  is  completed.  It  wil 
generally  be  necessary  for  a  time  to  regulate  the  discharge  of  steam 
from  the  boiler  tested,  by  means  of  the  stop-valve,  while  fires  are  being 
hauled  at  the  beginning  and  at  the  end  of  the  test,  in  order  to  keep 
the  steam  pressure  in  the  boiler  at  those  times  up  to  the  average  during 
the  test. 

11.  Alternate  Method.     Instead  of  the  Standard  method  above 


BOILER  ACCESSORIES  107 

described,  the  following  may  be  employed  where  local  conditions 
render  it  necessary : 

At  the  regular  time  for  slicing  and  cleaning  fires,  have  them 
burned  rather  low,  as  is  usual  before  cleaning,  and  then  thoroughly 
cleaned ;  note  the  amount  of  coal  left  on  the  grate  as  nearly  as  it  can 
be  estimated ;  note  the  pressure  of  steam  and  the  height  of  the  water- 
level — which  should  be  at  the  medium  height  to  be  carried  throughout 
the  test — at  the  same  time;  and  note  this  time  as  the  time  of  starting 
the  test.  Fresh  coal,  which  has  been  weighed,  should  now  be  fired. 
The  ash-pits  should  be  thoroughly  cleaned  at  once  after  starting. 
Before  the  end  of  the  test  the  fires  should  be  burned  low,  just  as  before 
the  start,  and  the  fires  cleaned  in  such  a  manner  as  to  leave  the  same 
amount  of  fire,  and  in  the  same  condition,  on  the  grates  as  at  the  start. 
The  water-level  and  steam  pressure  should  be  brought  to  the  same 
point  as  at  the  start,  and  the  time  of  the  ending  of  the  test  should  be 
noted  just  before  fresh  coal  is  fired. 

12.  Keep  the  Conditions  Uniform.  The  boiler  should  be  run 
continuously,  without  stopping  for  meal-times  or  for  rise  or  fall  of 
pressure  of  steam  due  to  change  of  demand  for  steam.  The  draught, 
being  adjusted  to  the  rate  of  evaporation  or  combustion  desired  before 
the  test  is  begun,  should  be  retained  constant  during  the  test,  by 
means  of  the  damper. 

If  the  boiler  is  not  connected  to  the  same  steam  pipe  with  other 
boilers,  an  extra  outlet  for  steam  with  valve  in  same  should  be  pro- 
vided, so  that  in  case  the  pressure  should  rise  to  that  at  which  the 
safety-valve  is  set,  it  may  be  reduced  to  the  desired  point  by  opening 
the  extra  outlet,  without  checking  the  fires. 

If  the  boiler  is  connected  to  a  main  steam  pipe  with  other  boilers, 
the  safety-valve  on  the  boiler  being  tested  should  be  set  a  few  pounds 
higher  than  those  of  the  other  boilers,  so  that  in  case  of  a  rise  in  pres- 
sure the  other  boilers  may  blow  off,  and  the  pressure  be  reduced  by 
closing  their  dampers,  allowing  the  damper  of  the  boiler  being  tested 
to  remain  open,  and  firing  as  usual. 

All  the  conditions  should  be  kept  as  nearly  uniform  as  possible, 
such  as  force  of  draught,  pressure  of  steam,  and  height  of  water.  The 
time  of  cleaning  the  fires  will  depend  upon  the  character  of  the  fuel, 
the  rapidity  of  combustion,  and  the  kind  of  grates.  When  very  good 
coal  is  used,  and  the  combustion  not  too  rapid,  a  ten-hour  test  may  be 


108  BOILER  ACCESSORIES 

run  without  any  cleaning  of  the  grates  other  than  just  before  the 
beginning  and  just  before  the  end  of  the  test.  But  in  case  the  grates 
have  to  be  cleaned  during  the  test,  the  intervals  between  one  cleaning 
and  another  should  be  uniform. 

13.  Keeping  the  Records.    The  coal  should  be  weighed  and 
delivered  to  the  fireman  in  equal  portions,  each  sufficient  for  about 
one  hour's  run;  and  a  fresh  portion  should  not  be  delivered  until  the 
previous  one  has  all  been  fired.     The  time  required  to  consume  each 
portion  should  be  noted,  the  time  being  recorded  at  the  instant  of 
firing  the  first  of  each  new  portion.     It  is  desirable  that  at  the  same 
time  the  amount  of  water  fed  into  the  boiler  be  accurately  noted  and 
recorded,  including  the  height  of  the  water  in  the  boiler  and  the 
average  pressure  of  steam  and  temperature  of  feed  during  the  time. 
By  thus  recording  the  amount  of  water  evaporated  by  successive 
portions  of  coal,  the  record  of  the  test  may  be  divided  into  several 
divisions,  if  desired,  at  the  end  of  the  test,  to  discover  the  degree  of 
uniformity  of  combustion,  evaporation,  and  economy  at  different 
stages  of  the  test. 

14.  Priming  Tests.    In  all  tests  in  which  accuracy  of  results  is 
important,  calorimeter  tests  should  be  made  of  the  percentage  of 
moisture  in  the  steam,  or  of  the  degree  of  superheating.     At  least 
ten  such  tests  should  be  made  during  the  trial  of  the  boiler,  or  so  many 
as  to  reduce  the  probable  average  error  to  less  than  one  per  cent; 
and  the  final  records  of  the  boiler  test  should  be  corrected  according 
to  the  average  results  of  the  calorimeter  tests. 

On  account  of  the  difficulty  of  securing  accuracy  in  these  tests, 
the  greatest  care  should  be  taken  in  the  measurements  of  weights  and 
temperatures.  The  thermometers  should  be  accurate  within  a  tenth 
of  a  degree;  and  the  scales  on  which  the  water  is  weighed,  to  with' n 
one-hundredth  of  a  pound. 

15.  As  each  fresh  portion  of  coal  is  taken  from  the  coal-pocket, 
a  representative  shovelful  should  be  selected  from  it  and  placed  in  a 
barrel  or  box,  to  be  kept  until  the  end  of  the  trial,  for  analysis.    The 
samples  should  then  be  thoroughly  mixed  and  broken.     This  sample 
should  be  put  in  a  pile,  and  carefully  quartered.     One  quarter  may 
then  be  put  in  another  pile,,  and  the  process  repeated  until  five  or  six 
pounds  remain.     One  portion  of  this  sample  is  to  be  used  for  the 


BOILER  ACCESSORIES  109 

determination  of  the  moisture  and  heating  value;  the  other,  for  chemi- 
cal analysis. 

16.  The  ashes  refuse  should  be  weighed  dry,  and  a  sample 
frequently  taken  to  show  the  amount  of  combustible  material  passing 
through  the  grate.     To  get  a  representative  ash  sample,  the  ash-pile 
should  be  quartered  as  required  for  the  coal. 

17.  The  quality  of  the  fuel  should  be  determined  by  heat  test,  by 
analysis,  or  by  both. 

18.  The  analysis  of  the  flue  gases  is  an  especially  valuable 
method  of  determining  the  relative  value  of  different  methods  of 
firing  or  of  different  kinds  of  furnaces.     Great  care  should  be  taken 
to  procure  average  samples,  since  the  combustion  of  the  gases  mav 
vary  at  different  points  in  the  flue ;  and  as  the  combustion  of  flue  gas 
is  liable  to  vary  from  minute  to  minute,  the  sample  of  gas  should  be 
drawn  through  a  considerable  period  of  time. 

19.  It  is  desirable  to  have  a  uniform  system  of  determining  and 
recording  the  quantity  of  smoke  produced.     This  is  usually  expressed 
in  percentages,  depending  upon  the  judgment  of  the  observer. 

20.  In  tests  for  the  purpose  of  scientific  research  in  which  the 
determination  of  all  variables  is  desirable,  certain  observations  should 
be  made  which  in  general  are  not  necessary — such  as  the  measure- 
ment of  air-supply,  the  determination  of  its  moisture,  the  determina- 
tion of  the  heat  loss  by  radiation,  the  infiltration  of  air  through  the 
setting,  etc. — but  as  these  determinations  are  rarely  undertaken,  no 
definite  instructions  are  here  given. 

21.  Two  methods  of  defining  and   calculating  the  efficiency  of 
the  boiler  are  recommended.     They  are: 

Heat    absorbed   per  pound   of  combustible 

(1)  Efficiency  of   the  boiler  =  ^n — ^~  ~T—  ~j — t — 

Calorific  value  of  one  pound  of  combustible 

Heat  absorbed  per. pound  of  coal 

(2)  Efficiency  of    boiler  and    grate  =  ~— = — ^ —  —5 — j — — .- 

Calorific  value  of  one  pound  of  coal 

The  first  of  these  is  the  one  usually  adopted. 

22.  An  approximate  statement  of  the  distribution  of  the  heating 
value  of  the  coal  among  the  several  items  of  heat  utilized,  may  be 
included  in  the  report  of  a  test  when  analyses  of  the  fuel  and  chimney 
gases  have  been  made. 

23.  Record   of  the  Test.    The  data  and  results  of  the  trial 
should  be  recorded  in  a  systematic  manner,  according  either  to  Table  1 


110  BOILER  ACCESSORIES 

(see  Vol.  XXI,  Transactions  of  the  American  Society  of  Mechanical 
Engineers),  or  Table  2,  taken  from  those  "Transactions." 

TABLE  2 
Data  and  Results  of  Evaporative  Test 

Arranged  in  accordance  with  the  short  form  advised  by  the  Boiler  Test  Committee 
of  the  American  Society  of  Mechanical  Engineers,  Code  of  1899: 

Made  by on boiler,  at 

To  determine 

Kind  of  fuel 

Kind  of  furnace 

Method  of    starting  and  stopping  the  test    (Standard  or  Alternate,  Arts.  X 

and  XI,  Code) 

Grate  surface . .  . . sq.  ft. 

Water-heating  surface "     " 

Superheating  surface "    " 

Total  Quantities 

1.  Date  of  Trial 

2.  Duration  of  Trial hours 

3.  Weight  of  coal  as  fired Ibs. 

4.  Percentage  of  moisture  in  coal per  cent 

5.  Total  weight  of  dry  coai  consumed Ibs. 

6.  Total  ash  and  refuse " 

7.  Percentage  of  ash  and  refuse  in  dry  coal per  cent 

8.  Total  weight  of  water  fed  to  boiler Ibs. 

9.  Water  actually  evaporated,  corrected   for  moisture   or 

superheat  in  steam " 

10.  Equivalent  water   evaporated  into  dry  steam  from  and 

at  212°  F " 

Hourly  Quantities 

11.  Dry  coal  consumed  per  hour Ibs. 

12.  Dry  coal  per  square  foot  of  grate  surface  per 

hour " 

13.  Water    evaporated    per    hour    corrected    for 

quality  of  steam " 

14.  Equivalent  evaporation  per  hour   from    and 

at  212°  F " 

15.  Equivalent  evaporation  per  hour  from  and  at 

212°  F.  per  square    foot   of    water-heating 

surface " 

Average  Pressures,  Temperatures,  Etc 

16.  Steam  pressure  by  gauge Ibs.  per  sq.  in. 

17.  Temperature  of  feed-water  entering  boiler degrees 

18.  Temperature  of  escaping  gases  from  boiler 

19.  Force  of  draught  between  damper  and  boiler.  .  .     ins.  of  water 

20.  Percentage  of  moisture  in  steam,  or  number  or 

degrees  of  superheating .per  oent  or  degrees 


BOILER  ACCESSORIES 


111 


Horse-Power 

21.  Horse-power  developed  (item  14  -~  34^) H.  P. 

22.  Builder  s  rated  horse-power " 

23.  Percentage  of  builder's  rated  horse-power  developed  .  .  .per  cent. 

Economic  Results 

24.  Water  apparently  evaporated  under  actual  conditions  per 

pound  of  coal  as  fired  (item  8  -f-  item  3) Ibs. 

25.  Equivalent    evaporation    from    and    at     212°   F.   per  pound 

of  coal  as  fired  (item  10  -f-  item  3) " 

26.  Equivalent  evaporation    from  and  at  212°  F.  per  pound  of 

dry  coal  (item  10  -j-  item  5) " 

27.  Equivalent  evaporation    from    and  at   212°  F.  per  pound  of 

combustible  [item  10  ~  (item  5  —  item  G)] " 

If  items  25,  26,  and  27. are  not  corrected  for  quality  of  steam,  the  fact  should  be 
stated. 

Efficiency 


28. 
29. 
30. 
31. 


•Calorific  value  of  the  dry  coal  per  pound B.  T.  IT. 

Calorific  value  of  the  combustible  per  pound " 

Efficiency  of  boiler  (based  on  combustible) per  cent. 

Efficiency  of  boiler,  including  grate  (based  on  dry  coal)        " 

Cost  of  Evaporation 

Cost  of  coal  per  ton  of  -    —  Ibs.  delivered  in  boiler-room     $ 

Cost  of  coal  required  for  evaporating  1.000  Ibs.  of  water 

from  and  at  212°  F 

A  log  of  the  test  should  be  kept  on  properly  prepared  blanks 
containing  headings  as  follows: 

TABLE  NO. 


PRESSURES 

TEMPERATURES 

FUEL, 

FEED-  WATER 

Fn 

&c 

O> 

"I 

o 

1 

(3 

TIME 

Baromet 

Steam  ga 

c3 

SO 

Q 

External 

Boiler-ro 

I 

e3 

1 

2 
3 

s 

Pounds 

1 

0 

Hi 

FIRING 

Starting  the  Fire.  The  fireman  should  first  ascertain  the  water- 
level;  as  the  gauge-glass  is  not  always  reliable,  on  account  of  im- 
purities, foam,  etc.,  the  gauge-cocks  should  be  tried.  In  a  batter}' 


112  BOILER  ACCESSORIES 

of  boilers,  the  gauge-cocks  of  each  should  be  opened,  for  the  water 
may  not  stand  at  the  same  level  in  each.  The  safety-valve  should  be 
raised  slightly  from  its  seat.  If  the  fire  has  been  banked  over  night, 
open  the  draughts,  and  rattle  down  the  ashes  and  clinkers  from  the 
grate.  In  case  the  fire  has  been  allowed  to  go  out,  a  new  one  may  be 
started  if  the  gauge-glass  shows  the  proper  amount  of  water,  and  the 
valves  work  well. 

If  anthracite  coal  is  used,  first  throw  a  thin  layer  of  coal  all  over 
the  grate,  then  place  a  piece  of  wood  across  the  mouth  of  the  furnace 
just  inside  the  door  and  lay  other  pieces  of  wood  at  right  angles  to 
the  cross-piece  with  the  ends  resting  on  it.  This  allows  a  space  under 
the  wood  for  air.  Now  throw  on  coal  until  the  wood  is  covered.  The 
fire  may  be  started  with  oily  cotton  waste,  shavings,  or  any  combustible 
material. 

Keep  the  furnace  door  open  and  the  draught-plate  closed  until 
the  wood  is  burning  freely,  which  causes  the  flame  to  pass  over  and 
through  the  coal  and  to  ignite  it.  The  fire  is  then  spread  or  pushed 
back  evenly  over  the  furnace  bars;  the  furnace  door  closed;  the  ash- 
pit door  opened,  as  the  draught  requires;  and  more  coal  added  when 
necessary  If  bituminous  coal  is  used,  do  not  spread  a  thin  layer  over 
the  grate  bars  under  the  wood. 

The  fire  at  the  start  should  be  slow,  to  cause  gradual,  uniform 
heating  of  the  water  and  various  parts  of  the  boiler.  If  steam  is 
raised  too  rapidly,  enormous  strains  are  set  up,  due  to  unequal  expan- 
sion, thereby  causing  leakage  at  joints,  and  perhaps  rupture. 

If  the  boiler  is  of  the  water-tube  type,  steam  may  be  raised  more 
rapidly,  because  the  amount  of  water  is  less  and  the  joints  are  usually 
placed  at  some  distance  from  the  intense  heat  of  the  fire. 

The  fire  being  started,  the  method  of  adding  coal  depends  upon 
the  fireman,  the  kind  of  coal,  the  type  of  boiler,,  and  the  rate  of  com- 
bustion. There  are  three  general  methods  of  firing — spreading, 
alternate  or  side  firing,  and  coking. 

Spreading  is  accomplished  by  placing  small  amounts  of  coal 
uniformly  over  the  entire  surface  of  the  grate  at  short  intervals.  By 
this  method,  the  coal  is  thrown  just  where  it  is  wanted  and  then  not 
disturbed.  The  fire  should  be  hollowed  in  the  center;  that  is,  it 
should  be  thicker  at  the  sides.  Good  results  are  obtained  from  this 
method,  since  the  fire  can  be  kept  in  the  right  condition  at  all  times, 


BOILER  ACCESSORIES  1 13 

if  the  coal  is  of  the  right  sort.  During  the  operation  of  firing,  the 
door  should  be  kept  open  as  little  as  possible,  or  the  fire  will  be  cooled 
by  the  entrance  of  cold  air.  For  a  short  time,  while  the  coal  is  giving 
off  gas,  the  draught-plate  of  the  furnace  door  should  be  opened,  in 
order  that  sufficient  air  may  be  admitted  above  the  coal  to  burn  the 
hydrocarbons. 

When  the  alternate  or  side  firing  method  is  used,  coal  is  spread 
so  as  to  cover  one  side  of  the  fire  completely  at  one  firing,  leaving  the 
other  side  bright.  At  the  next  firing,  the  bright  side  is  covered.  The 
hydrocarbons  given  off  by  the  fresh  coal  are  burned  by  the  hot  gases 
from  the  incandescent  coal.  This  method  is  superior  to  spreading, 
because  the  entire  furnace  is  not  cooled  off  by  the  addition  of  fresh 
fuel. 

Side  firing  is  most  advantageous  with  two  furnaces  leading  to 
a  common  combustion  chamber.  The  furnaces  are  fired  at  regular 
intervals  with  moderate  charges  of  coal,  and  the  draught-plates  are 
opened  while  the  coal  is  giving  off  gas. 

The  two  systems  described  above  are  best  adapted  to  anthracite 
coal,  since  it  burns  with  comparatively  little  smoke. 

With  bituminous  coal,  which  is  soft  and  burns  with  considerable 
smoke,  the  coking  method  is  used.  The  coal  is  piled  on  the  grate  just 
inside  the  door,  and  allowed  to  coke  from  15  to  30  minutes.  During 
this  time,  the  hydrocarbons  are  driven  off  and  burned  by  the  heat 
from  the  fire.  In  order  fully  to  accomplish  this,  air  must  be  admitted 
above  the  grate  through  the  draught-plates  of  the  furnace  door. 
The  coke  is  then  pushed  backward  over  the  fire,  and  a  new  supply 
placed  on  the  front  of  the  grate.  The  air  admitted  prevents  the  form- 
ing of  carbon  monoxide  gas  and  smoke.  At  the  same  time,  however,  it 
cools  the  furnace  somewhat  and  reduces  the  rate  of  evaporation;  but 
this  objection  is  not  serious  unless  a  boiler  must  be  worked  to  its  maxi- 
mum capacity  in  order  to  furnish  the  required  amount  of  steam.  If 
this  is  the  case,  economy  is  sacrificed  to  rapidity,  for  a  low  rate  of 
combustion  is  usually  more  economical  than  a  high  rate. 

The  necessary  thickness  of  a  bed  for  the  best  results,  is  found  by 
experiment.  It  depends  on  the  draught  and  the  kind  of  coal  used. 
If  the  former  is  strong,  and  the  coal  in  large  lumps,  the  bed  may  be 
thick  (about  one  foot);  but  if  the  draught  is  weak,  or  if  the  coal  is 
small,  the  bed  must  be  thin  (about  three  or  four  inches),  so  that  suffi- 


114  BOILER  ACCESSORIES 

cient  air  may  pass  through.  In  marine  and  locomotive  work,  with 
forced  draught,  the  bed  must  be  very  thick  to  get  a  large  coal  con- 
sumption per  square  foot  per  hour.  With  the  same  draught,  bitu- 
minous coal  can  be  fired  more  thickly  than  anthracite „ 

After  finding  from  experiment  the  best  thickness  for  the  bed,  keep 
it  at  that  thickness.  Always  keep  the  bed  of  uniform  thickness,  and 
never  let  the  fire  burn  holes  in  the  bed,  and  do  not  let  the  rear  of  the 
grate  become  bare.  If  a  larger  amount  of  steam  is  required,  fire 
smaller  quantities  at  more  frequent  intervals.  Do  not  fire  a  large 
amount  of  coal,  and  wait  for  the  pressure  to  rise;  The  firing  of  fresh 
coal  chills  the  furnace  and  temporarily  retards  combustion.  The 
coal  should  be  fired  in  small  quantities  and  as  quickly  as  possible. 
Keep  the  fire  free  from  ashes  and  clinkers,  but  do  not  clean  the  fires 
oftener  than  is  necessary. 

Four  tools  are  used  for  cleaning  the  fire — the  slice-bar,  the  prick- 
bar;  the  clinker  hook,  sometimes  called  the  devil's  claw;  and  the  hoe 
or  rake. 

.  The  slice-bar  is  a  long,  straight  bar,  with  the  end  flattened .  It 
is  used  to  break  up  clinkers  by  thrusting  it  between  the  grate  and  the 
fire.  It  is  also  used  to  break  up  caking  coaL  The  prick-bar  is  similar 
to  the  slice-bar,  except  that  the  end  is  bent  at  right  angles  like  a  hook. 
To  remove  ashes,  the  prick-bar  is  run  along,  up  between  the  grate 
bars,  from  underneath.  This  bar  is  often  made  with  detachable  hook, 
so  that  the  end  may  be  replaced  when  burned  off.  The  clinker  hook, 
or  devil's  claw,  is  used  to  haul  the  fire  forward.  The  hoe,  or  rake,  is 
used  to  draw  out  cinders,  to  haul  the  fire  forward,  etc. 

In  cleaning  the  fire,  the  fireman  first  looks  to  the  water  and  steam. 
There  should  be  enough  water  and  sufficient  steam  pressure  to  last 
during  cleaning.  Then  he  breaks  up  the  clinkers  with  the  slice-bar, 
and  removes  the  ashes  with  the  prick-bar.  If  necessary,  he  pushes  the 
fire  to  the  rear,  thoroughly  cleans  the  front  of  the  grate  bars,  and  then 
hauls  it  forward  and  cleans  the  back  of  the  furnace  bars.  Some  fire- 
men clean  one  side  at  a  time,  instead  of  first  the  front  and  then  the 
rear.  The  fire  should  be  allowed  to  burn  down  before  cleaning;  but 
sufficient  fuel,  called  chaff,  should  be  left  to  start  the  fire  quickly. 
Before  cleaning,  partly  close  the  dampers,  so  that  the  amount  of  cold  air 
admitted  will  be  small.  For  this  reason  and  to  prevent  loss  of  pressure, 
clean  as  rapidly  as  possible. 


BOILER  ACCESSORIES  115 

Banking  the  fire  depends  upon  the  condition  of  the  fire,  the 
fireman  himself,  and  the  length  of  time  it  is  to  remain  banked.  First 
clean  and  place  all  the  coal  in  a  small  space  at  the  bridge ;  then  cover 
with  fresh  coal  to  a  depth  depending  on  the  length  of  time  .the  fire 
is  to  remain  banked.  Then  close  all  dampers  and  open  the  door. 
Some  firemen  cover  the  front  of  the  furnace  bars  with  ashes. 

To  start  from  a  banked  fire,  first  examine  the  condition  of  the 
water-level,  steam  pressure,  safety-valves,  etc.  Then  clean  the  fire 
with  the  slice-bar,  and  rattle  down  the  ashes  with  the  prick-bar.  After 
spreading  the  coal  evenly  over  the  grate,  cover  with  a  thin  layer  of  coal, 
and  open  the  dampers. 

CARE  OF  BOILERS 

Any  amount  of  time  spent  in  the  proper  care  of  a  steam  boiler' 
will  be  amply  repaid,  for  this  is  of  great  importance.  The  boiler,  of 
course,  should  be  so  designed  and  constructed  that  all  parts  can  be 
inspected  readily;  but  this  is  of  little  benefit  unless  proper  and  rigid 
inspections  are  made.  All  internal  fittings,  such  as  fusible  plugs, 
water  alarms,  feed-pipes,  and  the  like,  should  occasionally  be  examined 
to  see  if  they  are  tight  and  in  good  working  order.  If  due  care  is  not 
given  to  the  boiler,  its  life  will  be  materially  shortened. 

The  following  rules  for  the  management  and  care  of  boilers  have 
been  established  by  the  Hartford  Steam  Boiler  Inspection  &  Insur- 
ance Company,  and  should  be  carefully  followed,  whether  the  boiler 
is  insured  by  the  above-mentioned  company  or  not: 

1.  Condition  of  Water.    The  first  duty  of  an  engineer,  when  he 
enters  his  boiler-room  in  the  morning,  is  to  ascertain  how  many  gauges 
of  water  there  are  in  his  boilers.     Never  unbank  or  replenish  the  fires 
until  this  is  done.     Accidents  have  occurred,  and  many  boilers  have 
been  entirely  ruined  from  neglect  of  this  precaution. 

2.  Low  Water.     In  case  of  low  water,  cover  the  fires  immedi- 
ately with  ashes;  or,  if  no  ashes  are  at  hand,  use  fresh  coal,  and  close 
ash-pit  doors.     Do  not  turn  on  the  feed  under  any  circumstances,  nor 
tamper  with  or  open  the  safety-valve.     Let  the  steam  outlets  remain 
as  they  are. 

3.  In  Case  of  Foaming.     Close  throttle,  and  keep  closed  long 
enough  to  show  true  level  of  water.     If  that  level  is  sufficiently  high, 
feeding  and  blowing  will  usually  suffice  to  correct  the  evil.     In  case 


116  BOILER  ACCESSORIES 

of  violent  foaming,  caused  by  dirty  water  or  by  change  from  salt  to 
fresh  water  or  vice  versa,  in  addition  to  the  action  above  stated,  check 
draught,  and  cover  fires  with  fresh  coal. 

4.  Leaks.     When  leaks  are  discovered,   they  should   be  re- 
paired as  soon  as  possible. 

5.  Blowing  Off.     Clean  furnace  and  bridge  wall  of  all  coal  and 
ashes.     Allow  brickwork  to  cool  down  for  two  hours  at  least  before 
opening  blow-off.     A  pressure  exceeding  20  Ibs.  should  not  be  allowed 
when  boilers  are  blown  out.     Blow  out  at  least  once  in  two  weeks. 
In  case  the  feed  becomes  muddy,  blow  out  six  or  eight  inches  every 
day.     When  surface  blow-cocks  are  used,  they  should  be  frequently 
opened  for  a  few  minutes  at  a  time. 

6.  Filling   Up  the  Boiler.      After  blowing  down,  allow  the 
boiler  to  become  cool  before  filling  again.     Cold  water  pumped  into 
hot  boilers  is  very  injurious,  from  the  sudden  contraction  set  up. 

7.  Exterior  of  Boiler.     Care  should  be  taken  that  no  water 
comes  in  contact  with  the  exterior  of  the  boiler,  either  from  leaky 
joints  or  from  other  causes. 

8.  Removing  Deposit  and  Sediment.     In  tubular  boilers,  the 
handholes    should  be  frequently  opened,  all  collections  removed,  and 
fore-plates  carefully  cleaned.     Also,  when  boilers  are  fed  in  front  and 
blown  off  through  the  same  pipe,  the  collection  of  mud  or  sediment  in 
the  rear  end  should  be  removed  frequently. 

9.  Safety= Valves.     Raise    the    safety-valves    cautiously    and 
frequently,  as  they  are  liable  to  become* fast  in  their  seats  and  useless 
for  the  purpose  intended. 

10.  Safety= Valve  and  Pressure=Qauge.     Should  the  gauge  at  any 
time  indicate    the    limit    of    pressure    allowed    by    the    insurance 
company,  see  that  thd  safety-valves  are  blowing  off.     In  case  of  dif- 
ference, notify  the  company's  inspector. 

11.  Qauge=Cocks,  Glass  Gauge.     Keep  gauge-cocks  clear  and 
in  constant  use.     Glass  gauges  should  not  be  relied  on  altogether. 

12.  Blisters.     When  a  blister  appears,  there  must  be  no  delay 
in  having  it  carefully  examined  and  trimmed  or  patched,  as  the  case 
may  require. 

13.  Clean  Sheets.     Particular  care  should  be  taken  to  keep 
sheets  and  parts  of  boilers  exposed  to  the  fire,  perfectly  clean;  also 


BOILER  ACCESSORIES  117 

all  tubes,  flues,  and  connections  well  swept.     This  is  particularly 
necessary  where  wood  or  soft  coal  is  used  for  fuel. 

14.  General  Care  of  Boilers  and  Connections.     Under  all  cir- 
cumstances, keep  the  gauges,  cocks,  etc.,  clean  and  in  good  order,  and 
things  generally  in  and  about  the  engine-room  in  a  neat  condition. 

15.  Getting   Up  Steam.     In  preparing  to  get  up  steam  after 
boilers  have  been  open  or  out  of  service,  great  care  should  be  exercised 
in  making  the  manhole  and  handhole  joints.     Safety-valve  should 
then  be  opened  and  blocked  open,  and  the  necessary  supply  of  water 
run  in  or  pumped  into  the  boilers,  until  it  shows  at  second  gauge  in 
tubular  and  locomotive  boilers;  a  higher  level  is  advisable  in  vertical 
tubulars  as  a  protection  to  the  top  ends  of  tubes.     After  this  is  done, 
fuel  may  be  placed  upon  the  grate,  dampers  opened,  and  fires  started. 
If  chimney  or  stack  is  cold  and  does  not  draw  properly,  burn  some 
oily  waste  or  light  kindling  at  the  base.     Start  fires  in  ample  time,  so 
that  it  will  not  be  necessary  to  urge  them  unduly.     When  steam 
issues  from  the  safety-valve,  lower  it  carefully  to  its  seat  and  note 
pressure  and  behavior  of  steam-gauge. 

If  there  are  other  boilers  in  operation,  and  stop-valves  are  to  be 
opened  to  place  boilers  in  connection  with  others  on  a  steam-pipe 
line,  watch  those  recently  fired  up,  until  pressure  is  up  to  that  of  the 
other  boilers  to  which  they  are  connected;  and,  when  that  pressure  is 
attained,  open  the  stop-valves  very  slowly  and  carefully. 


OK  THE 

UNIVERSITY 

OF 


INDEX 


Page 

Angle  valve _ 37 

Ashton  valve 44 

B 

Barrel  calorimeter G7 

Blow-out  apparatus 45 

Boiler  coverings 78 

Boiler  explosions 88 

causes  of 90 

defective  design 91 

defects  of  workmanship .  . 92 

deterioration 91 

low  water 90 

mismanagement 92 

energy,  determination  of 89 

investigation 93 

prevention 94 

Boiler  setting • 1 

Boiler  supports 6 

Boilers,  care  of 115 

blisters 116 

blowing  off 116 

clean  sheets 116 

condition  of  water 115 

exterior  of  boiler 116 

filling  up  boiler 1 16 

foaming. .  . 115 

gauge-cocks 116 

getting  up  steam 117 

leaks 116 

low  water 115 

removing  deposit  and  sediment.    116 

safety-valves 116 

Boilers,  horse-power  of 

Bucket  trap 64 

C 

Calorimeters 66 

barrel 67 

separator "0 

throttling 71 


120  INDEX 


Page 

Check  valves 38 

Circulating  apparatus 56 

Cochrane  feed- water  heater 59 

Cochrane  steam  separator 63 

Competition  valve 37 

Corrosion 81 

external '. 81 

internal 82 

D 

Dial  gauge 29 

Differential  steam  trap 65 

Down-draft  furnaces I ........  15 

Draft-gauge 22 

Drafts 22 

forced ,  •... .  .  22 

closed  ash-pit  system 23 

closed  stoke-hold  system 23 

Ellis  &  Eaves  system 24 

Howden  system 24 

induced  system 24 

natural 22 

E 

Eames  differential  draft-gauge 22 

Ellis  &  Eaves  system  of  forced  draft 24 

Equalizing  valve .; 66 

Evaporators 57 

External  corrosion 81 

F 

Feed  apparatus . . .  -. : 48 

circulating  apparatus ....;..  v ...  56 

evaporators 57 

feed-water  heaters ...  .Y. 58 

injectors  or  inspirators 54 

pumps 53 

Feed-water  heaters 58 

Firing.... .V ..' /. .  Ill 

Float  trap 64 

Forced  draft , 22 

Foster  reducing  valve 45 

Fuel  economizers 17 

Fuel  used  in  steam  production 94 

artificial  fuels 101 

charcoal 97 

coal ..  . .".' 94 

coke .,  ...  ...-.,.  ,;vW:-«  .....  97 

culm .:i 97 

gas 100 


INDEX  121 


Page 
Fuel  used  in  steam  production 

liquid  fuels 98 

peat 97 

straw 98 

wood 97 

Furnaces 7 

bridge 12 

door 9 

down-draft 15 

fuel  economizers 17 

fusible  plugs 20 

grate 9 

hollow  arch 15 

mechanical  stokers 19 

prevention  of  smoke 13 

special 12 

Fusible  plugs 20 

G 

Gate  valve 38 

Gauges 

steam  and  vacuum '. 29 

water 32 

Globe  valve 36 

Grates .  '. 9 

circular 10 

herring  bone 10 

rocking 11 

Grooving 83 

H 

Hancock  inspirator 55 

Handholes 29 

Herring  bone  grate 10 

Hollow  arch 15 

Holt  reducing  valve 45 

Horse-power  of  boilers 79 

Howden  system  of  forced  draft 24 

I 

Incrustation 84 

carbonate  of  lime 85 

corbonate  of  magnesia 86 

iron  salts 86 

sulphate  of  lime -  .  86 

Induced  draft 24 

Injectors  or  inspirators 54 

Hancock 55 

Internal  corrosion .* 82 


122  INDEX 

K 

Page 

Kelley  standard  rocking  grate 12 

"Klinger  Patent"  gauge-glass 35 

L 

Lagging ,.r. 75 

Lever  safety-valve 40 

M 

Manholes 28 

Mason  reducing  valve 45 

Mechanical  stokers 19 

Muffler  safety-valve 44 

N 

Natural  draft 22 

P 

Pipe  coverings 76 

Piping , 73 

Pitting 83 

Pop  regulator 43 

Pop  safety-valve 42 

Priming 61 

Pumps : .  . 53 

steam-driven : 53 

R 

Reducing  valves 44 

Foster 45 

Holt 45 

Mason 45 

Return  traps 66 

Rocking  grates 11 

S 

Safety-valves 39 

lever '.- 40 

muffler 44 

pop ;.  ..                             ...  42 

Scale  or  sludge 84 

Separator  calorimeter 70 

Smoke,  prevention  of .  . 13 

Star  Marine  pop  safety-valve 44 

Steam  boiler  trials 101 

alternate  method 106 

keeping  records 108 

preliminaries  to  a  test 104 

priming  tests 108 

record  of  test ~. 109 

standard  method ..-...'.- 106 

uniform  conditions.  . 107 


INDEX  123 


Page 

Steam  jets .' 25 

Steam  separators 62 

Cochrane 63 

Stratton 63 

Steam  traps 64 

bucket 64 

differential 65 

floaj 64 

return / 66 

Steam  and  vacuum  gauges .  .  .  29 

Stratton  steam  separator , 63 

T 
Tables 

coals,  analysis  and  heat  value  of  various 95 

evaporation,  factors  of : 80 

evaporative  test,  data  and  results  of 110 

gases,  evaporative  power  of 100 

heat,  relative  values  of  preventatives  of  radiation  of .  . 77 

heat  loss,  variation  of,  with  pressure 76 

heat  losses  in  bare  pipes 76 

log  of  test Ill 

Throttling  calorimeter 71 

Try-cocks 33 

Tube-cleaners 26 

Tube-stoppers 26 

V 

Valves 36 

angle. 37 

check 38 

gate 38 

globe 36 

materials  for 39 

reducing 44 

safety 39 

W 

Water  gauges 32 

gauge-glasses v  33 

try  cocks 33 

Water-tube  boilers 6 

Worthington  duplex  steam  pump 53 


